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# Page Tags and summary
1 Learn web development Beginner, CSS, HTML, Index, Intro, Landing, Learn, Web
Welcome to the MDN learning area. This set of articles aims to provide complete beginners to web development with all that they need to start coding simple websites.
2 Accessibility ARIA, Accessibility, Articles, Beginner, CSS, CodingScripting, HTML, JavaScript, Landing, Learn, Module
Learning some HTML, CSS, and JavaScript is useful if you want to become a web developer, but your knowledge needs to go further than just using the technologies — you need to use them responsibly so that you maximize the audience for your websites and don't lock anyone out of using them. To achieve this, you need to adhere to general best practices (which are demonstrated throughout the HTML, CSS, and JavaScript topics), do cross browser testing, and consider accessibility from the start. In this module, we'll cover the latter in detail.
3 Accessible multimedia Accessibility, Article, Audio, Beginner, CodingScripting, HTML, Images, JavaScript, Learn, Multimedia, Video, captions, subtitles, text tracks
This chapter has provided a summary of accessibility concerns for multimedia content, along with some practical solutions.
4 Assessment: Accessibility troubleshooting Accessibility, Assessment, Beginner, CSS, CodingScripting, HTML, JavaScript, Learn, WAI-ARIA
In the assessment for this module, we present to you a simple site with a number of accessibility issues that you need to diagnose and fix.
5 CSS and JavaScript accessibility best practices Accessibility, Article, CSS, CodingScripting, Guide, JavaScript, Learn, color, contrast, hiding, unobtrusive
We hope this article has given you a good amount of detail and understanding about the accessibility issues surrounding CSS and JavaScript use on web pages.
6 HTML: A good basis for accessibility AT, Accessibility, Article, Beginner, Buttons, CodingScripting, Forms, HTML, Learn, Links, a11y, assistive technology, keyboard, screenreader, semantics
You should now be well-versed in writing accessible HTML for most occasions. Our WAI-ARIA basics article will help to fill gaps in this knowledge, but this article has taken care of the basics. Next up we'll explore CSS and JavaScript, and how accessibility is affected by their good or bad use.
7 Mobile accessibility Accessibility, Article, Beginner, CodingScripting, Learn, Mobile, responsive, screenreader, touch
In this article we have provided you with some details about common mobile accessibility-specific issues and how to overcome them. We also took you through usage of the most common screenreaders to aid you in accessibility testing.
8 WAI-ARIA basics ARIA, Accessibility, Article, Beginner, CodingScripting, Guide, HTML, JavaScript, Learn, WAI-ARIA, semantics
This article has by no means covered all that's available in WAI-ARIA, but it should have given you enough information to understand how to use it, and know some of the most common patterns you will encounter that require it.
9 What is accessibility? AT, Accessibility, Article, Beginner, CSS, CodingScripting, HTML, JavaScript, Learn, Tools, Users, assistive technology, keyboard, screan reader, screenreader
This article should have given you a useful high-level overview of accessibility, shown you why it's important, and looked at how you can fit it into your workflow. You should now also have a thirst to learn about the implementation details that can make sites accessible, and we'll start on that in the next section, looking at why HTML is a good basis for accessibility.
10 Common questions CodingScripting, Infrastructure, Learn, Web, WebMechanics
This section of the Learning Area is designed to provide answers to common questions that may come up, which are not necessarily part of the structured core learning pathways (e.g. the HTML or CSS learning articles.) These articles are designed to work on their own.
11 How can we design for all types of users? Accessibility, Beginner, Design, Mobile, NeedsActiveLearning
When you're building a website, one top issue to consider is Universal Design: accommodating all users regardless of disability, technical constraints, culture, location, and so on.
12 How do I start to design my website? Beginner, Composing, NeedsActiveLearning, needsSchema
When starting with a web project, many people focus on the technical side. Of course you must be familiar with the technique of your craft, but what really matters is what you want to accomplish. Yes, it seems obvious, but too many projects fail not from a lack of technical know-how, but from lack of goals and vision.
13 How do I use GitHub Pages? Beginner, GitHub, Guide, Web, gh-pages, git, publish
GitHub is a "social coding" site. It allows you to upload code repositories for storage in the Git version control system. You can then collaborate on code projects, and the system is open-source by default, meaning that anyone in the world can find your GitHub code, use it, learn from it, and improve on it. You can do that with other people's code too! This article provides a basic guide to publishing content using Github's gh-pages feature.
14 How do you host your website on Google App Engine? Beginner, Google App Engine, Google Cloud Platform, Guide, Host, Learn, Web, publish, website
Google App Engine is a powerful platform that lets you build and run applications on Google’s infrastructure — whether you need to build a multi-tiered web application from scratch or host a static website. Here's a step-by-step guide to hosting your website on Google App Engine.
15 How do you make sure your website works properly? Beginner, Document, Guide, NeedsActiveLearning, Web, Web Development, WebMechanics, troubleshooting
So you've published your website online? Very good! But are you sure it works properly?
16 How do you set up a local testing server? Beginner, Express, Flask, Learn, Node, PHP, Python, django, lamp, server-side, servers
Throughout most of the learning area, we tell you to just open your examples directly in a browser — this can be done by double clicking the HTML file, dragging and dropping it into the browser window, or choosing File > Open... and navigating to the HTML file. There are many ways to achieve this.
17 How do you upload your files to a web server? Beginner, FTP, GitHub, Uploading, WebMechanics, hosting, rsync, sftp
If you have built a simple web page (see HTML basics for an example), you will probably want to put it online, on a web server. In this article we'll discuss how to do that, using various available options such as SFTP clients, RSync and GitHub.
18 How does the Internet work? Beginner, Tutorial, WebMechanics
The Internet is the backbone of the Web, the technical infrastructure that makes the Web possible. At its most basic, the Internet is a large network of computers which communicate all together.
19 How much does it cost to do something on the Web? Beginner, WebMechanics, cost, hosting, web development tools
When launching a website, you may spend nothing, or your costs may go through the roof. In this article we discuss how much everything costs, and how you get what you pay (or don't pay).
20 What HTML features promote accessibility? Accessibility, Beginner, HTML, Learn, NeedsContent
The following content describes specific features of HTML that can be used to make a web page more accessible to people with different disabilities.
21 What are browser developer tools? Beginner, Browser, CSS, CodingScripting, Dev Tools, HTML, JavaScript, Learn
The devtools live inside your browser in a subwindow that looks roughly like this, depending on what browser you are using:
22 What are hyperlinks? Beginner, Infrastructure, Navigation, NeedsActiveLearning
Hyperlinks, usually called links, are a foundational concept behind the Web. To explain what links are, we need to step back to the very basics of Web architecture.
23 What do common web layouts contain? Beginner, CSS, Design, HTML, NeedsActiveLearning
There's a reason we talk about web design. You start out with a blank page, and you can take it so many directions. And if you don't have much experience, starting out with a blank page might be a bit scary. We have over 25 years' experience and we'll give you some common rules of thumb to help you design your site.
24 What is a URL? Beginner, Infrastructure, NeedsActiveLearning, URL, resources, urls
With Hypertext and HTTP, URL is one of the key concepts of the Web. It is the mechanism used by browsers to retrieve any published resource on the web.
25 What is a domain name? Beginner, Domain names, Infrastructure, Intro, NeedsActiveLearning, Web
Domain names are a key part of the Internet infrastructure. They provide a human-readable address for any web server available on the Internet.
26 What is a web server? Beginner, Infrastructure, needsSchema
"Web server" can refer to hardware or software, or both of them working together.
27 What is accessibility? Accessibility, Beginner, Intro, NeedsActiveLearning, Web
Because of physical or technical limitations, maybe your visitors can't experience your website the way you hoped. In this article we give general accessibility principles and explain a few rules.
28 What is the difference between webpage, website, web server, and search engine? Beginner, NeedsActiveLearning, WebMechanics
As with any area of knowledge, the web comes with a lot of jargon. Don't worry, we won't overwhelm you with all of it (we have a glossary if you're curious). However, there are a few basic terms you need to understand at the outset, since you'll hear these expressions all the time as you read on. It's easy to confuse these terms sometimes since they refer to related but different functionalities. In fact, you'll sometimes see these terms misused in news reports and elsewhere, so getting them mixed up is understandable!
29 What software do I need to build a website? Beginner, NeedsActiveLearning, WebMechanics
You can download most of the programs you need for web development for free. We'll provide a few links in this article.
30 What text editors are available? Beginner, Composing, Guide, NeedsActiveLearning, Tools, text editor
A website consists mostly of text files, so for a fun, pleasant development experience you should choose your text editor wisely.
31 Getting started with the Web Beginner, CSS, Design, Guide, HTML, Index, l10n:priority, publishing, theory
It's a lot of work to create a professional website, so if you're new to web development, we encourage you to start small. You won't build another Facebook right away, but it's not hard to get your own simple website online, so we'll start there.
32 CSS basics Beginner, CSS, CodingScripting, Learn, Styling, Web, l10n:priority
Like HTML, CSS is not really a programming language. It is not a markup language either — it is a style sheet language. This means that it lets you apply styles selectively to elements in HTML documents. For example, to select all the paragraph elements on an HTML page and turn the text within them red, you'd write this CSS:
33 Dealing with files Beginner, CodingScripting, Files, Guide, HTML, l10n:priority, theory, website
When you are working on a website locally on your computer, you should keep all the related files in a single folder that mirrors the published website's file structure on the server. This folder can live anywhere you like, but you should put it somewhere where you can easily find it, maybe on your Desktop, in your Home folder, or at the root of your hard drive.
34 HTML basics Beginner, CodingScripting, HTML, Learn, Web, l10n:priority
HTML is not a programming language; it is a markup language that defines the structure of your content. HTML consists of a series of elements, which you use to enclose, or wrap, different parts of the content to make it appear a certain way, or act a certain way. The enclosing tags can make a word or image hyperlink to somewhere else, can italicize words, can make the font bigger or smaller, and so on.  For example, take the following line of content:
35 How the Web works Beginner, Client, DNS, HTTP, IP, Infrastructure, Learn, Server, TCP, l10n:priority
This theory is not essential to writing web code in the short term, but before long you'll really start to benefit from understanding what's happening in the background.
36 Installing basic software Beginner, Browser, Learn, Setup, Tools, WebMechanics, l10n:priority, text editor
That looks like a scary list, but fortunately, you can get started in web development without knowing anything about most of these. In this article, we'll just set you up with a bare minimum — a text editor and some modern web browsers.
37 JavaScript basics Beginner, CodingScripting, JavaScript, Learn, Web, l10n:priority
JavaScript ("JS" for short) is a full-fledged dynamic programming language that, when applied to an HTML document, can provide dynamic interactivity on websites. It was invented by Brendan Eich, co-founder of the Mozilla project, the Mozilla Foundation, and the Mozilla Corporation.
38 Publishing your website Beginner, CodingScripting, FTP, GitHub, Google App Engine, Learn, Web, l10n:priority, publishing, web server
Publishing a website isn't a simple topic, mainly because there are so many different ways to do it. In this article we don't aim to document all possible methods. Rather, we'll discuss the pros and cons of three broad strategies from a beginner's point of view, and then walk you through one method that will work for now.
39 What will your website look like? Assets, Beginner, Composing, Content, Deprecated, Design, Fonts, Learn, Simple, l10n:priority, step by step
Before doing anything, you need some ideas. What should your website actually do? A website can do basically anything, but, for your first try, you should keep things simple. We'll start by creating a simple webpage with a heading, an image, and a few paragraphs.
40 How to contribute to the Learning Area on MDN Beginner, Contribute, Documentation, Guide, Learn, MDN Meta, l10n:priority
On this page, you'll find everything you need to start helping improve MDN's learning content. There are many things you can do, depending on how much time you have and whether you are a beginner, a web developer, or a teacher.
41 Index Index, Learn, MDN Meta
Found 251 pages:
42 JavaScript Beginner, CodingScripting, JavaScript, JavaScripting beginner, Landing, Module, Topic, l10n:priority
JavaScript is a programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at—displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, or more—you can bet that JavaScript is probably involved.
43 Asynchronous JavaScript Beginner, CodingScripting, Guide, JavaScript, Landing, Promises, async, asynchronous, await, callbacks, requestAnimationFrame, setInterval, setTimeout
In this module we take a look at asynchronous JavaScript, why it is important, and how it can be used to effectively handle potential blocking operations such as fetching resources from a server.
44 Choosing the right approach Beginner, Intervals, JavaScript, Learn, Optimize, Promises, async, asynchronous, await, requestAnimationFrame, setInterval, setTimeout, timeouts
To finish this module off, we'll provide a brief discussion of the different coding techniques and features we've discussed throughout, looking at which one you should use when, with recommendations and reminders of common pitfalls where appropriate. We'll probably add to this resource as time goes on.
45 Cooperative asynchronous JavaScript: Timeouts and intervals Animation, Beginner, CodingScripting, Guide, Intervals, JavaScript, Loops, asynchronous, requestAnimationFrame, setInterval, setTimeout, timeouts
Here we look at the traditional methods JavaScript has available for running code asychronously after a set time period has elapsed, or at a regular interval (e.g. a set number of times per second), talk about what they are useful for, and look at their inherent issues.
46 General asynchronous programming concepts JavaScript, Learn, Promises, Threads, asynchronous, blocking
In this article we'll run through a number of important concepts relating to asynchronous programming, and how this looks in web browsers and JavaScript. You should understand these concepts before working through the other articles in the module.
47 Graceful asynchronous programming with Promises Beginner, CodingScripting, Guide, JavaScript, Learn, Promises, async, asynchronous, catch, finally, then
Promises are a comparatively new feature of the JavaScript language that allow you to defer further actions until after a previous action has completed, or respond to its failure.
48 Introducing asynchronous JavaScript Beginner, CodingScripting, Guide, Introducing, JavaScript, Learn, Promises, async, asynchronous, await, callbacks
In this article we briefly recap the problems associated with synchronous JavaScript, and take a first look at some of the different asynchronous techniques you'll encounter, showing how they can help us solve such problems.
49 Making asynchronous programming easier with async and await Beginner, CodingScripting, Guide, JavaScript, Learn, Promises, async, asynchronous, await
More recent additions to the JavaScript language are async functions and the await keyword, part of the so-called ECMAScript 2017 JavaScript edition (see ECMAScript Next support in Mozilla). These features basically act as syntactic sugar on top of promises, making asynchronous code easier to write and to read afterwards. They make async code look more like old-school synchronous code, so they're well worth learning. This article gives you what you need to know.
50 Client-side web APIs API, Articles, Beginner, CodingScripting, DOM, Graphics, JavaScript, Landing, Learn, Media, Module, WebAPI, data
When writing client-side JavaScript for web sites or applications, you will quickly encounter Application Programming Interfaces (APIs). APIs are programming features for manipulating different aspects of the browser and operating system the site is running on, or manipulating data from other web sites or services. In this module, we will explore what APIs are, and how to use some of the most common APIs you'll come across often in your development work.
51 Client-side storage API, Article, Beginner, CodingScripting, Guide, IndexedDB, JavaScript, Learn, Storage
That's it for now. We hope you've found our rundown of client-side storage technologies useful.
52 Drawing graphics API, Article, Beginner, Canvas, CodingScripting, Graphics, JavaScript, Learn, WebGL
At this point, you should have a useful idea of the basics of graphics programming using Canvas and WebGL and what you can do with these APIs, as well as a good idea of where to go for further information. Have fun!
53 Fetching data from the server API, Article, Beginner, CodingScripting, Fetch, JSON, JavaScript, Learn, Promises, Server, XHR, XML, XMLHttpRequest, data, request
This article shows how to start working with both XHR and Fetch to fetch data from the server.
54 Introduction to web APIs 3rd party, API, Article, Beginner, Browser, CodingScripting, Learn, Object, WebAPI, client-side
At this point, you should have a good idea of what APIs are, how they work, and what you can do with them in your JavaScript code. You are probably excited to start actually doing some fun things with specific APIs, so let's go! Next up, we'll look at manipulating documents with the Document Object Model (DOM).
55 Manipulating documents API, Article, Beginner, CodingScripting, DOM, Document, Document Object Model, JavaScript, Learn, Navigator, WebAPI, Window
We have reached the end of our study of document and DOM manipulation. At this point you should understand what the important parts of a web browser are with respect to controlling documents and other aspects of the user's web experience. Most importantly, you should understand what the Document Object Model is, and how to manipulate it to create useful functionality.
56 Third-party APIs 3rd party, API, Beginner, CodingScripting, Google Maps, Learn, NYTimes, Third party, youtube
This article has given you a useful introduction to using third-party APIs to add functionality to your websites.
57 Video and audio APIs API, Article, Audio, Beginner, CodingScripting, Guide, JavaScript, Learn, Video
I think we've taught you enough in this article. The HTMLMediaElement API makes a wealth of functionality available for creating simple video and audio players, and that's only the tip of the iceberg. See the "See also" section below for links to more complex and interesting functionality.
58 Introducing JavaScript objects Article, Assessment, Beginner, CodingScripting, Guide, JavaScript, Learn, Objects, Tutorial
In JavaScript, most things are objects, from core JavaScript features like strings and arrays to the browser APIs built on top of JavaScript. You can even create your own objects to encapsulate related functions and variables into efficient packages, and act as handy data containers. The object-based nature of JavaScript is important to understand if you want to go further with your knowledge of the language, therefore we've provided this module to help you. Here we teach object theory and syntax in detail, then look at how to create your own objects.
59 Adding features to our bouncing balls demo Assessment, Beginner, CodingScripting, JavaScript, Learn, OOJS, Object-Oriented, Objects, l10n:priority
In this assessment, you are expected to use the bouncing balls demo from the previous article as a starting point, and add some new and interesting features to it.
60 Inheritance in JavaScript Article, Beginner, CodingScripting, Constructor, Function, Getter, Inheritance, JavaScript, Learn, OOJS, OOP, Object, Object member, Prototype, extends, l10n:priority, setter
This article has covered the remainder of the core OOJS theory and syntax that we think you should know now. At this point you should understand JavaScript object and OOP basics, prototypes and prototypal inheritance, how to create classes (constructors) and object instances, add features to classes, and create subclasses that inherit from other classes.
61 JavaScript object basics API, Article, Beginner, CodingScripting, JavaScript, Learn, Object, Syntax, bracket notation, dot notation, instance, l10n:priority, object literal, theory, this
Congratulations, you've reached the end of our first JS objects article — you should now have a good idea of how to work with objects in JavaScript — including creating your own simple objects. You should also appreciate that objects are very useful as structures for storing related data and functionality — if you tried to keep track of all the properties and methods in our person object as separate variables and functions, it would be inefficient and frustrating, and we'd run the risk of clashing with other variables and functions that have the same names. Objects let us keep the information safely locked away in their own package, out of harm's way.
62 Object building practice Article, Beginner, Canvas, CodingScripting, Guide, JavaScript, Learn, Objects, Tutorial, l10n:priority
We hope you had fun writing your own real world random bouncing balls example, using various object and object-oriented techniques from throughout the module! This should have given you some useful practice in using objects, and good real world context.
63 Object prototypes Article, Beginner, CodingScripting, Constructor, JavaScript, Learn, OOJS, OOP, Object, Prototype, Prototype Chaining, create(), l10n:priority
This article has covered JavaScript object prototypes, including how prototype object chains allow objects to inherit features from one another, the prototype property and how it can be used to add methods to constructors, and other related topics.
64 Object-oriented JavaScript for beginners Article, Beginner, CodingScripting, Constructor, Create, JavaScript, Learn, OOJS, OOP, Object, Object-Oriented, instance, l10n:priority
This article has provided a simplified view of object-oriented theory — this isn't the whole story, but it gives you an idea of what we are dealing with here. In addition, we have started to look at different ways of generating object instances.
65 Working with JSON Article, Beginner, CodingScripting, Guide, JSON, JSON API, JSON Arrays, JSON parsing, JSON structure, JavaScript, Learn, Objects, Tutorial, l10n:priority
In this article, we've given you a simple guide to using JSON in your programs, including how to create and parse JSON, and how to access data locked inside it. In the next article, we'll begin looking at object-oriented JavaScript.
66 JavaScript First Steps Arrays, Article, Assessment, Beginner, CodingScripting, Guide, JavaScript, Landing, Module, Numbers, Operators, Variables, l10n:priority, maths, strings
In our first JavaScript module, we first answer some fundamental questions such as "what is JavaScript?", "what does it look like?", and "what can it do?", before moving on to taking you through your first practical experience of writing JavaScript. After that, we discuss some key building blocks in detail, such as variables, strings, numbers and arrays.
67 A first splash into JavaScript Article, Beginner, CodingScripting, Conditionals, Functions, JavaScript, Learn, Objects, Operators, Variables, events, l10n:priority
Now you've learned something about the theory of JavaScript, and what you can do with it, we are going to give you a crash course in the basic features of JavaScript via a completely practical tutorial. Here you'll build up a simple "Guess the number" game, step by step.
68 Arrays Arrays, Article, Beginner, CodingScripting, JavaScript, Join, Learn, Pop, Push, l10n:priority, shift, split, unshift
In the final article of this module, we'll look at arrays — a neat way of storing a list of data items under a single variable name. Here we look at why this is useful, then explore how to create an array, retrieve, add, and remove items stored in an array, and more besides.
69 Basic math in JavaScript — numbers and operators Article, Beginner, CodingScripting, Guide, JavaScript, Learn, Math, Operators, augmented, increment, l10n:priority, maths, modulo
In this article we have covered the fundamental information you need to know about numbers in JavaScript, for now. You'll see numbers used again and again, all the way through your JavaScript learning, so it's a good idea to get this out of the way now. If you are one of those people that doesn't enjoy math, you can take comfort in the fact that this chapter was pretty short.
70 Handling text — strings in JavaScript Article, Beginner, CodingScripting, Guide, JavaScript, Join, Quotes, concatenation, l10n:priority, strings
Next, we'll turn our attention to strings — this is what pieces of text are called in programming. In this article, we'll look at all the common things that you really ought to know about strings when learning JavaScript, such as creating strings, escaping quotes in strings, and joining strings together.
71 Silly story generator Arrays, Assessment, Beginner, CodingScripting, JavaScript, Learn, Numbers, Operators, Variables, l10n:priority, strings
In this assessment you'll be tasked with taking some of the knowledge you've picked up in this module's articles and applying it to creating a fun app that generates random silly stories. Have fun!
72 Storing the information you need — Variables Arrays, Booleans, JavaScript, Numbers, Objects, Updating, Variables, declaring, initializing, l10n:priority, loose typing, strings
By now you should know a reasonable amount about JavaScript variables and how to create them. In the next article, we'll focus on numbers in more detail, looking at how to do basic math in JavaScript.
73 Useful string methods Article, Beginner, CodingScripting, JavaScript, Learn, case, indexof, l10n:priority, length, lower, replace, split, upper
Now that we've looked at the very basics of strings, let's move up a gear and start thinking about what useful operations we can do on strings with built-in methods, such as finding the length of a text string, joining and splitting strings, substituting one character in a string for another, and more.
74 What is JavaScript? 3rd party, API, Article, Beginner, Browser, CodingScripting, Core, JavaScript, Learn, Script, comments, external, inline, l10n:priority, what
So there you go, your first step into the world of JavaScript. We've begun with just theory, to start getting you used to why you'd use JavaScript and what kind of things you can do with it. Along the way, you saw a few code examples and learned how JavaScript fits in with the rest of the code on your website, amongst other things.
75 What went wrong? Troubleshooting JavaScript Article, Beginner, CodingScripting, Debugging, Developer Tools, Error, JavaScript, Learn, Tutorial, console.log, l10n:priority
So there we have it, the basics of figuring out errors in simple JavaScript programs. It won't always be that simple to work out what's wrong in your code, but at least this will save you a few hours of sleep and allow you to progress a bit faster when things don't turn out right earlier on in your learning journey.
76 JavaScript building blocks Article, Assessment, Beginner, CodingScripting, Conditionals, Functions, Guide, Introduction, JavaScript, Landing, Loops, Module, events, l10n:priority
In this module, we continue our coverage of all JavaScript's key fundamental features, turning our attention to commonly-encountered types of code block such as conditional statements, loops, functions, and events. You've seen this stuff already in the course, but only in passing — here we'll discuss it all explicitly.
77 Build your own function Article, Beginner, CodingScripting, Functions, Guide, JavaScript, Learn, Tutorial, build, invoke, l10n:priority, parameters
With most of the essential theory dealt with in the previous article, this article provides practical experience. Here you will get some practice building your own, custom function. Along the way, we'll also explain some useful details of dealing with functions.
78 Function return values Article, Beginner, CodingScripting, Functions, Guide, JavaScript, Learn, Return, Return values, l10n:priority
There's one last essential concept for us to discuss in this course, to close our look at functions — return values. Some functions don't return a significant value after completion, but others do, and it's important to understand what their values are, how to make use of them in your code, and how to make your own custom functions return useful values. We'll cover all of these below.
79 Functions — reusable blocks of code API, Article, Beginner, Browser, CodingScripting, Custom, Functions, Guide, JavaScript, Learn, Method, anonymous, invoke, l10n:priority, parameters
Another essential concept in coding is functions, which allow you to store a piece of code that does a single task inside a defined block, and then call that code whenever you need it using a single short command — rather than having to type out the same code multiple times. In this article we'll explore fundamental concepts behind functions such as basic syntax, how to invoke and define them, scope, and parameters.
80 Image gallery Assessment, Beginner, CodingScripting, Conditionals, Event Handler, JavaScript, Learn, Loops, events, l10n:priority
Now that we've looked at the fundamental building blocks of JavaScript, we'll test your knowledge of loops, functions, conditionals and events by getting you to build a fairly common item you'll see on a lot of websites — a JavaScript-powered image gallery.
81 Introduction to events Article, Beginner, CodingScripting, Event Handler, Guide, JavaScript, Learn, events, l10n:priority
Events are actions or occurrences that happen in the system you are programming, which the system tells you about so you can respond to them in some way if desired. For example, if the user clicks a button on a webpage, you might want to respond to that action by displaying an information box. In this article, we will discuss some important concepts surrounding events, and look at how they work in browsers. This won't be an exhaustive study; just what you need to know at this stage.
82 Looping code Article, Beginner, CodingScripting, DO, Guide, JavaScript, Learn, Loop, break, continue, for, l10n:priority, while
Programming languages are very useful for rapidly completing repetitive tasks, from multiple basic calculations to just about any other situation where you've got a lot of similar items of work to complete. Here we'll look at the loop structures available in JavaScript that handle such needs.
83 Making decisions in your code — conditionals Article, Beginner, CodingScripting, Conditionals, JavaScript, Learn, Switch, conditions, else, if, l10n:priority, ternary
In any programming language, the code needs to make decisions and carry out actions accordingly depending on different inputs. For example, in a game, if the player's number of lives is 0, then it's game over. In a weather app, if it is being looked at in the morning, show a sunrise graphic; show stars and a moon if it is nighttime. In this article, we'll explore how so-called conditional statements work in JavaScript.
84 Solve common problems in your JavaScript code Beginner, JavaScript, Learn
The following links point to solutions to common everyday problems you'll need to fix in order to get your JavaScript code to run correctly.
85 Learn to style HTML using CSS Beginner, CSS, CodingScripting, Debugging, Landing, NeedsContent, Style, Topic, length, specificity
Cascading Stylesheets — or CSS — is the first technology you should start learning after HTML. While HTML is used to define the structure and semantics of your content, CSS is used to style it and lay it out. For example, you can use CSS to alter the font, color, size, and spacing of your content, split it into multiple columns, or add animations and other decorative features.
86 CSS layout Beginner, CSS, Floating, Grids, Guide, Landing, Layout, Learn, Module, Multiple column, Positioning, alignment, flexbox, float, table
At this point we've already looked at CSS fundamentals, how to style text, and how to style and manipulate the boxes that your content sits inside. Now it's time to look at how to place your boxes in the right place in relation to the viewport, and one another. We have covered the necessary prerequisites so we can now dive deep into CSS layout, looking at different display settings, modern layout tools like flexbox, CSS grid, and positioning, and some of the legacy techniques you might still want to know about.
87 Flexbox Article, Beginner, CSS, CSS layouts, CodingScripting, Flexible Boxes, Guide, Layout, Layouts, Learn, flexbox
That concludes our tour of the basics of flexbox. We hope you had fun, and will have a good play around with it as you travel forward with your learning. Next we'll have a look at another important aspect of CSS layouts — CSS Grids.
88 Floats Article, Beginner, CSS, Clearing, CodingScripting, Floats, Guide, Layout, columns, multi-column
You now know all there is to know about floats in modern web develoment. See the article on legacy layout methods for information on how they used to be used, which may be useful if you find yourself working on older projects.
89 Fundamental Layout Comprehension Assessment, Beginner, CSS, Layout, Learn
If you have worked through this module then you will have already covered the basics of what you need to know to do CSS layout today, and to work with older CSS as well. This task will test some of your knowledge by way of developing a simple webpage layout using a variety of techniques.
90 Grids Article, Beginner, CSS, CSS Grids, CodingScripting, Grids, Guide, Layout, Learn, Tutorial, grid design, grid framework, grid system
In this overview we have toured the main features of CSS Grid Layout. You should be able to start using it in your designs. To dig further into the specification, read our guides to Grid Layout, which can be found below.
91 Introduction to CSS layout Article, Beginner, CSS, Floats, Grids, Introduction, Layout, Learn, Positioning, Tables, flexbox, flow
This article has provided a brief summary of all the layout technologies you should know about. Read on for more information on each individual technology!
92 Legacy layout methods Beginner, CSS, Floats, Guide, Layout, Learn, grid system, legacy
You now understand how various grid systems are created, which will be useful in working with older sites and in understanding the difference between the native grid of CSS Grid Layout and these older systems.
93 Multiple-column layout Beginner, CSS, Guide, Layout, Learn, Learning, Multi-col, Multiple columns
You now know how to use the basic features of multiple-column layout, another tool at your disposal when choosing a layout method for the designs you are building.
94 Normal Flow float, grid
Now that you understand normal flow, and how the browser lays things out by default, move on to understand how to change this default display to create the layout needed by your design.
95 Positioning Article, Beginner, CSS, CodingScripting, Guide, Layout, Positioning, absolute, fixed, relative
I'm sure you had fun playing with basic positioning; while it is not a method you would use for entire layouts, as you can see there are many tasks it is suited for.
96 Practical positioning examples Article, Beginner, CSS, CodingScripting, Guide, Layout, Learn, absolute, fixed, relative
So that rounds off our look at positioning — by now, you should have an idea of how the basic mechanics work, as well as understanding how to start applying these to build some interesting UI features. Don't worry if you didn't get this all immediately — positioning is a fairly advanced topic, and you can always work through the articles again to aid your understanding. The next subject we'll turn to is Flexbox.
97 Supporting older browsers Beginner, CSS, Guide, Layout, Learn, feature queries, flexbox, float, grid, legacy
You now have the knowledge to confidently use techniques such as Grid and Flexbox, create fallbacks for older browsers, and make use of any new techniques that might come along in the future.
98 Introduction to CSS Beginner, CSS, Cascade, CodingScripting, Inheritance, Introduction to CSS, Landing, Module, Selectors, color, properties, rules, units
CSS (Cascading Style Sheets) is used to style and layout web pages — for example, to alter the font, colour, size and spacing of your content, split it into multiple columns, or add animations and other decorative features. This module gets you started on the path to CSS mastery with the basics of how it works, including selectors and properties, writing CSS rules, applying CSS to HTML, how to specify length, colour, and other units in CSS, cascade and inheritance, and debugging CSS.
99 Attribute selectors Article, Attribute, Attribute selectors, Beginner, CSS, Guide, Learn, Selectors
Attribute selectors are a special kind of selector that will match elements based on their attributes and attribute values. Their generic syntax consists of square brackets ([]) containing an attribute name followed by an optional condition to match against the value of the attribute. Attribute selectors can be divided into two categories depending on the way they match attribute values: Presence and value attribute selectors and Substring value attribute selectors.
100 CSS Selectors Article, Beginner, CSS, Class, Element, Guide, Learn, Pseudo-class, Pseudo-element, Selectors, combinator, id, universal
In CSS, selectors are used to target the HTML elements on our web pages that we want to style. There are a wide variety of CSS selectors available, allowing for fine grained precision when selecting elements to style. In the next few articles we'll run through the different types in great detail, seeing how they work.
101 CSS syntax Beginner, CSS, CodingScripting, Selectors, Syntax, blocks, comments, declarations, rules, shorthand, whitespace
Next up, we dive into CSS syntax in a lot more detail, looking at how properties and their values form into declarations, multiple declarations form into declaration blocks, and declaration blocks and selectors form into complete CSS rules. We round off the article by looking at other CSS syntax features such as comments and whitespace.
102 CSS values and units Article, Beginner, CSS, CSS Colors, CSS Units, CodingScripting, Functions, Guide, HTML Colors, HTML Styles, Styling HTML, color, length, units
We hope you enjoyed learning about CSS values and units — don't worry if this doesn't all make complete sense right now; you'll get more and more practice with this fundamental part of CSS syntax as you move forward!
103 Cascade and inheritance Article, Beginner, CSS, Cascade, CodingScripting, Guide, Inheritance, Layout, Learn, Style, Stylesheets, importance, source order, specificity
In this article we will define what the CSS cascade is, what specificity is, what importance is, and how properties inherit from different rules.
104 Combinators and selector lists Article, Beginner, CSS, Guide, Learn, Selectors
In our final article on selectors, we'll explore combinators and groups of selectors — two ways of combining multiple selectors together for further useful selection capabilities.
105 Debugging CSS Article, CSS, CSS editor, CodingScripting, DOM inspector, Debugging, Guide, Page Inspector, linting, validator
Well done for completing the last article of the first CSS module! Now that you've come this far, you can have a go at completing our CSS assessment, and then start exploring some other CSS and HTML modules.
106 Fundamental CSS comprehension Assessment, Beginner, CSS, CodingScripting, Selectors, Style, Syntax, box model, comments, rules
You've covered a lot in this module, so it must feel good to have reached the end! The final step before you move on is to attempt the assessment for the module — this involves a number of related exercises that must be completed in order to create the final design — a business card/gamer card/social media profile.
107 How CSS works CSS, CodingScripting, DOM, Guide, Link, Syntax, external, internal, line
CSS (Cascading Style Sheets) allows you to create great looking web pages, but how does it work under the hood? This article explains what CSS is, how the browser turns HTML into a Document Object Model (DOM), how CSS is applied to parts of the DOM, some very basic syntax examples, and what code is used to actually include our CSS in our web page.
108 Pseudo-classes and pseudo-elements Article, Beginner, CSS, Guide, Learn, Pseudo, Pseudo-class, Pseudo-element, Selectors
In this, the third in our series of articles on selectors, we discuss pseudo-selectors. These don't select elements, but rather certain parts of elements, or elements only in certain contexts. They come in two main types: pseudo-classes and pseudo-elements.
109 Simple selectors Article, Beginner, CSS, CSS Class, Guide, Learn, Selectors
In this, our first selectors article, we'll learn about "simple" selectors. They directly match one or more elements of a document, based on the type of element, class, or id.
110 The box model Article, Beginner, Block, Boxes, CSS, CodingScripting, Content, Guide, Learn, Learning, Model, background clip, border, box, height, inline, margin, overflow, padding, width
The CSS box model is the foundation of layout on the Web — each element is represented as a rectangular box, with the box's content, padding, border, and margin built up around one another like the layers of an onion. As a browser renders a web page layout, it works out what styles are applied to the content of each box, how big the surrounding onion layers are, and where the boxes sit in relation to one another. Before understanding how to create CSS layouts, you need to understand the box model — this is what we'll look at in this article.
111 Styling boxes Beginner, Boxes, CSS, CodingScripting, Landing, Module, Tables, backgrounds, borders, effects
Hello and welcome to Styling CSS boxes — in the last module we looked at the content inside your boxes; in this module, we'll look at styling the actual box itself, by manipulating background color and images, borders, and other parts of the box. We'll also look at other topics, from making HTML tables look good to applying advanced effects like filters and blend modes.
112 A cool looking box Assessment, Beginner, CSS, Learn, backgrounds, borders, box, box model, effects
In this assessment, you'll get some more practice in creating cool-looking boxes by trying to create an eye-catching box.
113 Advanced box effects Article, Beginner, Blend modes, Boxes, CSS, CodingScripting, Filters, Styling, box shadows, effects
We hope this article was fun — playing with shiny toys generally is, and it is always interesting to see what kinds of tools are just becoming available in cutting edge browsers. You've reached the end of the Styling boxes articles, so next up you'll test your box styling skills with our assessments.
114 Box model recap Article, Beginner, Boxes, CSS, CodingScripting, Guide, Layout, box model
We looked at the basics of the CSS box model in our Introduction to CSS module. This article will provide a recap, and dive into some further details on the subject.
115 Changing background styles using CSS Article, Beginner, CSS, CodingScripting, Gradients, Guide, Images, Position, attachment, backgrounds, colors
This article should have taught you most of what you'll ever need to know about styling element backgrounds. Hopefully you'll have had some fun along the way too! In the next article we'll play with borders, and look at how to style those.
116 Creating fancy letterheaded paper Assessment, Background, Beginner, Boxes, CSS, CodingScripting, border, box, letter, letterhead, letterheaded, paper
If you want to make the right impression, writing a letter on nice letterheaded paper can be a really good start. In this assessment we'll challenge you to create an online template to achieve such a look.
117 Styling borders using CSS Article, Beginner, CSS, CodingScripting, Guide, Images, Radius, border, borders, radii
Now you understand borders, right? Not the ones at the edges of your country, but the ones at the edges of your elements. Borders are useful to understand, and have many different uses. In the article that follows, we'll take a sideways step, and explore best practices for styling tables — this will show a useful application of some of the techniques we've looked at so far in the module.
118 Styling tables Article, Beginner, CSS, CodingScripting, Guide, NeedsUpdate, Styling, Tables
With the dizzy exciting heights of styling tables now behind us, we need something else to occupy our time. Never fear — the next chapter provides a look at some advanced box effects, some of which have only landed in browsers very recently (such as blend modes and filters), and some of which are a bit more established (such as box shadows.)
119 Styling text Beginner, CSS, CodingScripting, Fonts, Landing, Links, Module, Text, font, letter, line, lists, shadow, web fonts
With the basics of the CSS language covered, the next CSS topic for you to concentrate on is styling text — one of the most common things you'll do with CSS. Here we look at text styling fundamentals, including setting font, boldness, italics, line and letter spacing, drop shadows and other text features. We round off the module by looking at applying custom fonts to your page, and styling lists and links.
120 Fundamental text and font styling Article, Beginner, CSS, Guide, Style, Text, alignment, family, font, shorthand, spacing, weight
We hoped you enjoyed playing with text in this article! The next article will give you all you need to know about styling HTML lists.
121 Styling links Article, Beginner, CSS, Focus, Guide, Learn, Links, Pseudo-class, hover, hyperlinks, menus, tabs
We hope this article has provided you with all you'll need to know about links — for now! The final article in our Styling text module details how to use custom fonts on your websites, or web fonts as they are better known.
122 Styling lists Article, Beginner, CSS, Guide, Styling, Text, bullets, lists
Lists are relatively easy to get the hang of styling once you know a few associated basic principles and specific properties. In the next article we'll get on to link styling techniques.
123 Typesetting a community school homepage Assessment, Beginner, CSS, CodingScripting, Link, Styling text, font, list, web font
In this assessment we'll test your understanding of all the text styling techniques we've covered throughout this module by getting you to style the text for a community school's homepage. You might just have some fun along the way.
124 Web fonts @font-face, Article, Beginner, CSS, CSS Fonts, Fonts, Guide, Learn, Web Development, Web Fonts Article, Web fonts documentation, font-family, web fonts
Now that you have worked through our articles on text styling fundamentals, it is time to test your comprehension with our assessment for the module, Typesetting a community school homepage.
125 Use CSS to solve common problems Beginner, CSS, Learn
The following links provide solutions to common problems you can solve with CSS.
126 CSS FAQ CSS, Example, FAQ, Guide, Web, questions
In this article, you'll find some frequently-asked questions (FAQs) about CSS, along with answers that may help you on your quest to become a web developer.
127 Using CSS generated content Basic, Beginner, CSS, CSS:Getting_Started, Graphics, Guide, NeedsUpdate, Web
This is the 9th section of the CSS Getting Started tutorial; it describes some ways in which you can use CSS to add content when a document is displayed. You modify your stylesheet to add text content and an image.
128 create fancy boxes Beginner, CSS, CodingScripting, Learn
CSS boxes are the building blocks of any web page styled with CSS. Making them nice looking is both fun and challenging. It's fun because it's all about turning a design idea into working code; It's challenging because of annoying constraints and crazy freedom in the use of CSS. Let's do some fancy boxes.
129 Learning HTML: Guides and tutorials Beginner, Guide, HTML, Intro, Learn, Topic
To build websites, you should know about HTML — the fundamental technology used to define the structure of a webpage. HTML is used to specify whether your web content should be recognized as a paragraph, list, heading, link, image, multimedia player, form, or one of many other available elements or even a new element that you define.
130 Forms and buttons Article, Assessment, Beginner, Controls, Forms, HTML, Landing, Learn, Validation, semantics
Forms and buttons are a very important part of the Web — these allow your site visitors to input data and send it to you (e.g. registration, login and feedback forms), and you to implement controls for controlling complex functionality (for example submitting a form to the server, or pausing playback of a video.) This module gets you started.
131 Form and button basics Article, Beginner, Buttons, Controls, Forms, HTML, Learn
In this article we'll take you through the basics of HTML forms, including their purpose, basic features, and common form controls. We'll also have a look at HTML buttons and how they can be used.
132 HTML Cheatsheet Beginner, Guide, HTML
While using HTML it can be very handy to have an easy way to remember how to use HTML tags properly and how to apply them. MDN provides you with an extended HTML documentation as well as a deep instructional HTML how-to. However, in many cases we just need some quick hints as we go. That's the whole purpose of the cheatsheet, to give you some quick accurate ready to use code snippets for common usages.
133 HTML Tables <td>, <th>, <tr>, Article, Beginner, CodingScripting, Guide, HTML, Landing, Module, Tables
A very common task in HTML is structuring tabular data, and it has a number of elements and attributes for just this purpose. Coupled with a little CSS for styling, HTML makes it easy to display tables of information on the web such as your school lesson plan, the timetable at your local swimming pool, or statistics about your favorite dinosaurs or football team. This module takes you through all you need to know about structuring tabular data using HTML.
134 Assessment: Structuring planet data Assessment, Beginner, CodingScripting, HTML, Learn, Tables
In our table assessment, we provide you with some data on the planets in our solar system, and get you to structure it into an HTML table.
135 HTML table advanced features and accessibility Accessibility, Advanced, Article, Beginner, CodingScripting, HTML, Headers, Learn, caption, nesting, scope, sumary, table, tbody, tfoot, thead
There are a few other things you could learn about table HTML, but we have really given all you need to know at this moment in time. At this point, you might want to go and learn about styling HTML tables — see Styling Tables.
136 HTML table basics Article, Beginner, CodingScripting, HTML, Learn, Tables, basics, cell, col, colgroup, colspan, header, row, rowspan
That just about wraps up the basics of HTML Tables. In the next article we will look at some slightly more advanced table features, and start to think how accessible they are for visually impaired people.
137 HTML forms Beginner, Featured, Forms, Guide, HTML, Landing, Learn, Web
This module provides a series of articles that will help you master HTML forms. HTML forms are a very powerful tool for interacting with users; however, for historical and technical reasons, it's not always obvious how to use them to their full potential. In this guide, we'll cover all aspects of HTML forms, from structure to styling, from data handling to custom widgets.
138 Advanced styling for HTML forms Advanced, CSS, Example, Forms, Guide, HTML, Web
In this article, we will see how to use CSS with HTML forms to style some form widgets that are difficult to customize.
139 Form data validation Example, Forms, Guide, HTML, Intermediate, JavaScript, Web, regex
Form validation helps us to ensure that users fill out forms in the correct format, making sure that submitted data will work successfully with our applications. This article leads you through basic concepts and examples about form validation. For more information beyond this tutorial, see the Constraint validation guide.
140 HTML forms in legacy browsers Example, Forms, Guide, HTML, Intermediate, Web
All web developers learn very quickly (and sometimes painfully) that the Web is a very rough place for them. Our worst curse is legacy browsers. Okay, let's admit it, when we said "legacy browser" we all have in mind old versions of Internet Explorer ... but it's far from the only one. A one-year-old Firefox such as the ESR version is a legacy browser too. And in the mobile world? When neither the browser nor the OS can be updated? Yes, there are many older Android phones or iPhones that have stock browsers that are not up to date. These are also legacy browsers.
141 How to build custom form widgets Advanced, Example, Forms, Guide, HTML, Web
There are many cases where available HTML form widgets are just not enough. If you want to perform advanced styling on some widgets such as the <select> element or if you want to provide custom behaviors, you have no choice but to build your own widgets.
142 Example 1 Forms, Guide, HTML
This is the first example of code that explains how to build a custom form widget.
143 Example 2 Forms, HTML
This is the second example that explain how to build custom form widgets.
144 Example 3 Forms, HTML
This is the third example that explain how to build custom form widgets.
145 Example 4 Advanced, Example, Forms, Guide, HTML, Web
This is the fourth example that explain how to build custom form widgets.
146 Example 5 Forms, HTML
This is the last example that explain how to build custom form widgets.
147 How to structure an HTML form Beginner, CodingScripting, Example, Forms, Guide, HTML, Learn, Structure, Web
You now have all the knowledge you'll need to properly structure your HTML forms; the next article will dig into implementing all the different types of form widgets you'll want to use to collect information from your users.
148 Example Beginner, CSS, Example, Guide, HTML, Intro, Reference
This the example for a basic payment form for the article How to structure an HTML form.
149 Property compatibility table for form widgets Advanced, CSS, Forms, Guide, HTML, Junk, NeedsUpdate, Web
The following compatibility tables try to summarize the state of CSS support for HTML forms. Due to the complexity of CSS and HTML forms, these tables can't be considered a perfect reference. However, they will give you good insight into what can and can't be done, which will help you learn how to do things.
150 Sending form data Beginner, CodingScripting, Files, Forms, Guide, HTML, HTTP, Headers, Security, Web
This article looks at what happens when a user submits a form — where does the data go, and how do we handle it when it gets there? We also look at some of the security concerns associated with sending form data.
151 Sending forms through JavaScript Advanced, Example, Forms, Forms Guide, Guide, HTML, HTML forms, JavaScript, Learn, Security, Web, Web Forms
HTML forms can send an HTTP request declaratively. But forms can also prepare an HTTP request to send via JavaScript. This article explores ways to do that.
152 Styling HTML forms CSS, Example, Forms, Guide, HTML, Intermediate, Web
In this article, the user will learn how to use CSS with HTML forms to make them (hopefully) more beautiful. Surprisingly, this can be a little bit tricky.
153 The native form widgets Beginner, Controls, Example, Forms, Guide, HTML, Intermediate, Web, Widgets
We now look at the functionality of the different form widgets in detail, looking at what options are available to collect different types of data. This guide is somewhat exhaustive, covering all of the available native form widgets.
154 Your first HTML form Beginner, CodingScripting, Example, Forms, Guide, HTML, Learn, Web
Congratulations, you've built your first HTML form. It looks like this live:
155 Example Beginner, CodingScripting, Example, Forms, Guide, HTML, Learn, Web
This is the example code for the article Your first HTML form.
156 Introduction to HTML CodingScripting, HTML, Introduction to HTML, Landing, Links, Structure, Text, head, semantics
At its heart, HTML is a fairly simple language made up of elements, which can be applied to pieces of text to give them different meaning in a document (Is it a paragraph? Is it a bulleted list? Is it part of a table?), structure a document into logical sections (Does it have a header? Three columns of content? A navigation menu?), and embed content such as images and videos into a page. This module will introduce the first two of these, and introduce fundamental concepts and syntax you need to know to understand HTML.
157 Advanced text formatting Beginner, CodingScripting, Guide, HTML, Learn, Text, abbreviation, description list, quote, semantic
That marks the end of our study of HTML text semantics. Bear in mind that what you have seen during this course is not an exhaustive list of HTML text elements — we wanted to try to cover the essentials, and some of the more common ones you will see in the wild, or at least might find interesting. To find way more HTML elements, you can take a look at our HTML element reference (the Inline text semantics section would be a great place to start.) In the next article we will look at the HTML elements you'd use to structure the different parts of an HTML document.
158 Creating hyperlinks Beginner, CodingScripting, Guide, HTML, HTTP, Learn, Links, Title, absolute, href, hyperlinks, relative, urls
That's it for links, for now anyway! You'll return to links later on in the course when you start to look at styling them. Next up for HTML, we'll return to text semantics and look at some more advanced/unusual features that you'll find useful — Advanced text formatting is your next stop.
159 Debugging HTML Beginner, CodingScripting, Debugging, Error, Guide, HTML, Validation, validator
So there we have it, an introduction to debugging HTML, which should give you some useful skills to count on when you start to debug CSS, JavaScript, and other types of code later on in your career. This also marks the end of the Introduction to HTML module learning articles — now you can go on to testing yourself with our assessments: the first one is linked below.
160 Document and website structure Beginner, CodingScripting, Guide, HTML, Layout, Page, Site, blocks, semantics
At this point you should have a better idea about how to structure a web page/site. In the last article of this module, we'll study how to debug HTML.
161 Getting started with HTML Attribute, Beginner, CodingScripting, Comment, Element, Guide, HTML, entity reference, whitespace
You've reached the end of the article — we hope you enjoyed your tour of the very basics of HTML! At this point you should understand what the language looks like, how it works at a basic level, and be able to write a few elements and attributes. This is a perfect place to be right now, as in subsequent articles in the module we will go into some of the things you have already looked at in a lot more detail, and introduce some new features of the language. Stay tuned!
162 HTML text fundamentals Beginner, CodingScripting, Guide, HTML, Introduction to HTML, Learn, Text, headings, paragraphs, semantics
That's it for now! This article should have given you a good idea of how to start marking up text in HTML, and introduced you to some of the most important elements in this area. There are a lot more semantic elements to cover in this area, and we'll look at a lot more in our 'More Semantic Elements' article, later on in the course. In the next article, we'll be looking in detail at how to create hyperlinks, possibly the most important element on the Web.
163 Marking up a letter Assessment, Beginner, CodingScripting, HTML, Links, Text, head
We all learn to write a letter sooner or later; it is also a useful example to test out our text formatting skills! In this assessment you'll be given a letter to mark up to test basic and advanced HTML text formatting skills, including hyperlinks, plus we'll test your familiarity with some HTML <head> contents.
164 Structuring a page of content Assessment, Beginner, CodingScripting, Design, HTML, Layout, Learn, Structure, semantics
Structuring a page of content ready for laying it out using CSS is a very important skill to master, so in this assessment you'll be tested on your ability to think about how a page might end up looking, and choose appropriate structural semantics to build a layout on top of.
165 What’s in the head? Metadata in HTML Beginner, CodingScripting, Guide, HTML, Meta, favicon, head, lang, metadata
That marks the end of our quickfire tour of the HTML head — there's a lot more you can do in here, but an exhaustive tour would be boring and confusing at this stage, and we just wanted to give you an idea of the most common things you'll find in there for now! In the next article we'll be looking at HTML text fundamentals.
166 Multimedia and Embedding Assessment, Audio, Beginner, CodingScripting, Embedding, Flash, Guide, HTML, Images, Landing, Learn, Multimedia, SVG, Video, Web, iframes, imagemaps, img, responsive
We've looked at a lot of text so far in this course, but the web would be really boring only using text. Let's start looking at how to make the web come alive with more interesting content! This module explores how to use HTML to include multimedia in your web pages, including the different ways that images can be included, and how to embed video, audio, and even entire webpages.
167 Adding vector graphics to the Web Beginner, Graphics, Guide, HTML, Images, Learn, Raster, SVG, Vector, iframe, img
This article has provided you with a quick tour of what vector graphics and SVG are, why they are useful to know about, and how to include SVG inside your webpages. It was never intended to be a full guide to learning SVG, just a pointer so you know what SVG is if you meet it in your travels around the Web. So don't worry if you don't feel like you are an SVG expert yet. We've included some links below that might help you if you wish to go and find out more about how it works.
168 From object to iframe — other embedding technologies Article, Beginner, CodingScripting, Embedding, Flash, Guide, HTML, Learn, Multimedia and embedding, Object, embed, iframe
The topic of embedding other content in web documents can quickly become very complex, so in this article, we've tried to introduce it in a simple, familiar way that will immediately seem relevant, while still hinting at some of the more advanced features of the involved technologies. To start with, you are unlikely to use embedding for much beyond including third-party content like maps and videos on your pages. As you become more experienced, however, you are likely to start finding more uses for them.
169 Images in HTML Article, Beginner, Guide, HTML, Image, JPEG, PNG, alt text, captions, figcaption, figure, img, scr
In the beginning, the Web was just text, and it was really quite boring. Fortunately, it wasn't too long before the ability to embed images (and other more interesting types of content) inside web pages was added. There are other types of multimedia to consider, but it is logical to start with the humble <img> element, used to embed a simple image in a webpage. In this article we'll look at how to use it in depth, including the basics, annotating it with captions using <figure>, and detailing how it relates to CSS background images.
170 Mozilla splash page Assessment, Beginner, CodingScripting, Embedding, HTML, Images, JPEG, Multimedia, PNG, Video, iframe, img, picture, responsive, sizes, src, srcset
In this assessment, we'll test your knowledge of some of the techniques discussed in this module's articles, getting you to add some images and video to a funky splash page all about Mozilla!
171 Responsive images Article, Beginner, CodingScripting, Design, Graphics, Guide, HTML, Image, Intermediate, JPEG, PNG, Pictures, captions, hyperlinks, img, picture, sizes, src, srcset
That's a wrap for responsive images — we hope you enjoyed playing with these new techniques. As a recap, there are two distinct problems we've been discussing here:
172 Video and audio content Article, Audio, Beginner, Guide, HTML, Video, captions, subtitles, track
And that's a wrap; we hope you had fun playing with video and audio in web pages! In the next article, we'll look at other ways of embedding content on the Web, using technologies like <iframe> and <object>.
173 Use HTML to solve common problems CodingScripting, HTML
The following links point to solutions to common everyday problems you'll need to solve with HTML.
174 Add a hitmap on top of an image Graphics, Guide, HTML, Intermediate, Navigation
When you nest an image inside <a>, the entire image links to one webpage. An image map, on the other hand, contains several active regions (called "hotspots") that each link to a different resource.
175 Define terms with HTML Beginner, Guide, HTML, Learn
When you need a term defined, you probably go straight to a dictionary or glossary. Dictionaries and glossaries formally associate keywords with one or more descriptions, as in this case:
176 Tips for authoring fast-loading HTML pages Advanced, Guide, HTML, NeedsUpdate, Performance, Web, Web Performance
These tips are based on common knowledge and experimentation.
177 Use JavaScript within a webpage Beginner, HTML, JavaScript, OpenPractices
JavaScript is a programming language mostly used client-side to make webpages interactive. You can create amazing webpages without JavaScript, but JavaScript opens up a whole new level of possibilities.
178 Using data attributes Custom Data Attributes, Example, Guide, HTML, HTML5, Web
HTML5 is designed with extensibility in mind for data that should be associated with a particular element but need not have any defined meaning. data-* attributes allow us to store extra information on standard, semantic HTML elements without other hacks such as non-standard attributes, extra properties on DOM, or Node.setUserData().
179 Server-side website programming Beginner, CodingScripting, Intro, Landing, Learn, Server, Server-side programming, Topic
The Dynamic Websites  Server-side programming topic is a series of modules that show how to create dynamic websites; websites that deliver customised information in response to HTTP requests. The modules provide a general introduction to server-side programming, along with specific beginner-level guides on how to use the Django (Python) and Express (Node.js/JavaScript) web frameworks to create basic applications.
180 Django Web Framework (Python) Beginner, CodingScripting, Intro, Learn, Python, Server-side programming, django
Django is an extremely popular and fully featured server-side web framework, written in Python. The module shows you why Django is one of the most popular web server frameworks, how to set up a development environment, and how to start using it to create your own web applications.
181 Assessment: DIY Django mini blog Assessment, Beginner, CodingScripting, Learn, Server-side programming, blog, django, server-side
In this assessment you'll use the Django knowledge you've picked up in the Django Web Framework (Python) module to create a very basic blog.
182 Django Tutorial Part 10: Testing a Django web application Beginner, CodingScripting, Django Testing, Testing, Tutorial, django, server-side, tests, unit tests
Writing test code is neither fun nor glamorous, and is consequently often left to last (or not at all) when creating a website. It is however an essential part of making sure that your code is safe to release after making changes, and cost-effective to maintain.
183 Django Tutorial Part 11: Deploying Django to production Beginner, CodingScripting, Deployment, Django deployment, django, web server
That's the end of this tutorial on setting up Django apps in production, and also the series of tutorials on working with Django. We hope you've found them useful. You can check out a fully worked-through version of the source code on Github here.

The next step is to read our last few articles, and then complete the assessment task.
184 Django Tutorial Part 2: Creating a skeleton website Article, Beginner, CodingScripting, Guide, Intro, Learn, Tutorial, django, server-side
You have now created a complete skeleton website project, which you can go on to populate with urls, models, views, and templates.
185 Django Tutorial Part 3: Using models Article, Beginner, CodingScripting, Learn, Model, Tutorial, data, django, server-side
In this article we've learned how models are defined, and then used this information to design and implement appropriate models for the LocalLibrary website.
186 Django Tutorial Part 4: Django admin site Article, Beginner, CodingScripting, Learn, Python, Tutorial, django, django_admin, server-side
That's it! You've now learned how to set up the administration site in both its simplest and improved form, how to create a superuser, and how to navigate the admin site and view, delete, and update records. Along the way you've created a bunch of Books, BookInstances, Genres and Authors that we'll be able to list and display once we create our own view and templates.
187 Django Tutorial Part 5: Creating our home page Article, Beginner, CodingScripting, Learn, Tutorial, django, django templates, django views, server-side
We just created the home page for our site — an HTML page that displays a number of records from the database and links to other yet-to-be-created pages. Along the way we learned fundamental information about url mappers, views, querying the database with models, passing information to a template from a view, and creating and extending templates.
188 Django Tutorial Part 6: Generic list and detail views Beginner, Learn, Tutorial, django, django templates, django views
Congratulations, our basic library functionality is now complete!
189 Django Tutorial Part 7: Sessions framework Article, Beginner, CodingScripting, Learn, Python, Server, Tutorial, django, django sessions, server-side, sessions
You now know how easy it is to use sessions to improve your interaction with anonymous users.
190 Django Tutorial Part 8: User authentication and permissions Article, Authentication, Beginner, Forms, Learn, Permissions, Python, Server, Tutorial, django, django authentication, server-side, sessions
Excellent work — you've now created a website that library members can log in into and view their own content and that librarians (with the correct permission) can use to view all loaned books and their borrowers. At the moment we're still just viewing content, but the same principles and techniques are used when you want to start modifying and adding data.
191 Django Tutorial Part 9: Working with forms Beginner, CodingScripting, Django Forms, Forms, HTML forms, Learn, Tutorial, django, server side
Creating and handling forms can be a complicated process! Django makes it much easier by providing programmatic mechanisms to declare, render, and validate forms. Furthermore, Django provides generic form editing views that can do almost all the work to define pages that can create, edit, and delete records associated with a single model instance.
192 Django Tutorial: The Local Library website Article, Beginner, CodingScripting, Guide, Learn, Tutorial, django, server-side
Now that you know a bit more about the LocalLibrary website and what you're going to learn, it's time to start creating a skeleton project to contain our example.
193 Django introduction Beginner, CodingScripting, Intro, Learn, Python, Server-side programming, django
Congratulations, you've completed the first step in your Django journey! You should now understand Django's main benefits, a little about its history, and roughly what each of the main parts of a Django app might look like. You should have also learned a few things about the Python programming language, including the syntax for lists, functions, and classes.
194 Django web application security Article, Beginner, CodingScripting, Learn, Python, Security, Server-side programming, Web security, django, server-side
Django has effective protections against a number of common threats, including XSS and CSRF attacks. In this article we've demonstrated how those particular threats are handled by Django in our LocalLibrary website. We've also provided a brief overview of some of the other protections.
195 Setting up a Django development environment Beginner, Development environment, Installing, Intro, Learn, Python, django
You now have a Django development environment up and running on your computer.
196 Express web framework (Node.js/JavaScript) Beginner, CodingScripting, Express, Express.js, Intro, JavaScript, Learn, Node, Server-side programming, node.js
Express is a popular unopinionated web framework, written in JavaScript and hosted within the Node.js runtime environment. The module explains some of the key benefits of this framework, how to set up your development environment and how to perform common web development and deployment tasks.
197 Express Tutorial Part 2: Creating a skeleton website Beginner, CodingScripting, Development environment, Express, Intro, Learn, Node, npm, server-side
You have now created a skeleton website project for the Local Library and verified that it runs using node. Most importantly, you also understand how the project is structured, so you have a good idea where we need to make changes to add routes and views for our local library.
198 Express Tutorial Part 3: Using a Database (with Mongoose) Beginner, CodingScripting, Database, Express, Learn, Node, ODM, mongoose, nodejs, orm, server-side
In this article, we've learned a bit about databases and ORMs on Node/Express, and a lot about how Mongoose schema and models are defined. We then used this information to design and implement Book, BookInstance, Author and Genre models for the LocalLibrary website.
199 Express Tutorial Part 4: Routes and controllers Beginner, CodingScripting, Express, Express routes, Learn, Routes, nodejs, server-side
We've now created all the routes for our site, along with dummy controller functions that we can populate with a full implementation in later articles. Along the way we've learned a lot of fundamental information about Express routes, and some approaches for structuring our routes and controllers.
200 Express Tutorial Part 5: Displaying library data Beginner, Controller, Express, Learn, Template, View, nodejs, pug
We've now created all the "read-only" pages for our site: a home page that displays counts of instances of each of our models, and list and detail pages for our books, book instances, authors, and genres. Along the way, we've gained a lot of fundamental knowledge about controllers, managing flow control when using asynchronous operations, creating views using Pug, querying the database using our models, how to pass information to a template from your view, and how to create and extend templates. Those who completed the challenge will also have learned a little about date handling using moment.
201 Asynchronous flow control using async Express, Node, displaying data, part 5, server-side
The controller code for some of our LocalLibrary pages will depend on the results of multiple asynchronous requests, which may be required to run either in some particular order or in parallel. In order to manage flow control, and render pages when we have all the required information available, we'll use the popular node async module.
202 Author detail page Express, Node, displaying data, part 5, server-side
The author detail page needs to display the information about the specified Author, identified using their (automatically generated) _id field value, along with a list of all the Book objects associated with that Author.
203 Author list page and Genre list page challenge Express, Node, displaying data, part 5, server-side
The author list page needs to display a list of all authors in the database, with each author name linked to its associated author detail page. The date of birth and date of death should be listed after the name on the same line.
204 Book detail page Express, Node, displaying data, part 5, server-side
The Book detail page needs to display the information for a specific Book, identified using its (automatically generated) _id field value, along with information about each associated copy in the libary (BookInstance). Wherever we display an author, genre, or book instance, these should be linked to the associated detail page for that item.
205 Book list page Express, Node, displaying data, part 5, server-side
Next we'll implement our book list page. This page needs to display a list of all books in the database along with their author, with each book title being a hyperlink to its associated book detail page.
206 BookInstance detail page and challenge Express, Node, displaying data, part 5, server-side
The BookInstance detail page needs to display the information for each BookInstance, identified using its (automatically generated) _id field value. This will include the Book name (as a link to the Book detail page) along with other information in the record.
207 BookInstance list page Express, Node, displaying data, part 5, server-side
Next we'll implement our list of all book copies (BookInstance) in the library. This page needs to include the title of the Book associated with each BookInstance (linked to its detail page) along with other information in the BookInstance model, including the status, imprint, and unique id of each copy. The unique id text should be linked to the BookInstance detail page.
208 Date formatting using moment Express, Node, displaying data, part 5, server-side
The default rendering of dates from our models is very ugly: Tue Dec 06 2016 15:49:58 GMT+1100 (AUS Eastern Daylight Time). In this section we'll show how you can update the BookInstance List page from the previous section to present the due_date field in a more friendly format: December 6th, 2016.
209 Genre detail page Express, Node, displaying data, part 5, server-side
The genre detail page needs to display the information for the particular genre instance using its automatically generated _id field value as the identifier. The page should display the genre name, and a list of all books in the genre with links to each book's details page.
210 Home page Development, Express, Express Server, Node, displaying data, nodejs, part 5, server-side
The first page we'll create will be the website home page, which is accessible from either the site ('/') or catalog (catalog/) root. This will display some static text describing the site, along with dynamically calculated "counts" of different record types in the database.
211 LocalLibrary base template Express, Node, displaying data, part 5, server-side
Now that we understand how to extend templates using Pug, let's start by creating a base template for the project. This will have a sidebar with links for the pages we hope to create across the tutorial articles (e.g. to display and create books, genres, authors, etc.) and a main content area that we'll override in each of our individual pages.
212 Template primer Express, Node, displaying data, part 5, server-side
A template is a text file defining the structure or layout of an output file, with placeholders used to represent where data will be inserted when the template is rendered (in Express, templates are referred to as views).
213 Express Tutorial Part 6: Working with forms Beginner, CodingScripting, Express, Forms, HTML forms, Learn, Node, server-side
Express, node, and third-party packages on NPM provide everything you need to add forms to your website. In this article, you've learned how to create forms using Pug, validate and sanitize input using express-validator, and add, delete, and modify records in the database.
214 Create Author form Express, Forms, Node, part 6, server-side
EdiThis subarticle shows how to define a page for creating Author objects.
215 Create Book form Express, Forms, Node, part 6, server-side
EditThis subarticle shows how to define a page/form to create Book objects. This is a little more complicated than the equivalent Author or Genre pages because we need to get and display available Author and Genre records in our Book form.
216 Create BookInstance form Express, Forms, Node, part 6, server-side
EdiThis subarticle shows how to define a page/form to create BookInstance objects. This is very much like the form we used to create Book objects.
217 Create genre form Express, Forms, Node, part 6, server-side
This sub article shows how we define our page to create Genre objects (this is a good place to start because the Genre has only one field, its name, and no dependencies). Like any other pages, we need to set up routes, controllers, and views.
218 Delete Author form Express, Forms, Node, server-side
This subarticle shows how to define a page to delete Author objects.
219 Update Book form Express, Forms, Node, part 6, server-side
EditThis final subarticle shows how to define a page to update Book objects. Form handling when updating a book is much like that for creating a book, except that you must populate the form in the GET route with values from the database.
220 Express Tutorial Part 7: Deploying to production Beginner, CodingScripting, Deployment, Express, Learn, Node, heroku, server-side
That's the end of this tutorial on setting up Express apps in production, and also the series of tutorials on working with Express. We hope you've found them useful. You can check out a fully worked-through version of the source code on Github here.
221 Express Tutorial: The Local Library website Beginner, CodingScripting, Express, Intro, Learn, Node, Tutorial, nodejs, server-side
Now that you know a bit more about the LocalLIbrary website and what you're going to learn, it's time to start creating a skeleton project to contain our example.
222 Express/Node introduction Beginner, CodingScripting, Express, Learn, Node, nodejs, server-side
Congratulations, you've completed the first step in your Express/Node journey! You should now understand Express and Node's main benefits, and roughly what the main parts of an Express app might look like (routes, middleware, error handling, and template code). You should also understand that with Express being an unopinionated framework, the way you pull these parts together and the libraries that you use are largely up to you!
223 Installing LocalLibrary on PWS/Cloud Foundry Beginner, Cloud Foundry, CodingScripting, Deployment, Express, Learn, Node, PWS, Pivotal, production, server-side
If you followed the above steps, you should have now deployed the LocalLibrary app to PWS. Well done! If the deployment wasn't successful, double check all the steps.
224 Setting up a Node development environment Beginner, CodingScripting, Development environment, Express, Intro, Learn, Node, nodejs, npm, server-side
You now have a Node development environment up and running on your computer that can be used for creating Express web applications. You've also seen how NPM can be used to import Express into an application, and also how you can create applications using the Express Application Generator tool and then run them.
225 Node.js server without a framework JavaScript, NeedsContent, Node, Server, no framework
This article provides a simple static file server built with pure Node.js without the use of a framework.
226 Server-side website programming first steps Beginner, CodingScripting, Guide, Intro, Landing, Learn, Server-side programming
we answer a few fundamental questions about server-side programming — "What is it?", "How does it differ from client-side programming?", and "Why is it so useful?".
227 Client-Server Overview Beginner, CodingScripting, Guide, Intro, Learn, Server, Server-side programming
At this point you should have a good overview of the operations that server-side code has to perform, and know some of the ways in which a server-side web framework can make this easier.
228 Introduction to the server side Beginner, CodingScripting, Guide, Intro, Learn, Server, Server-side programming
Congratulations, you've reached the end of the first article about server-side programming.
229 Server-side web frameworks Beginner, CodingScripting, Guide, Intro, Learn, Server, Server-side programming, Web frameworks
This article has shown that web frameworks can make it easier to develop and maintain server-side code. It has also provided a high level overview of a few popular frameworks, and discussed criteria for choosing a web application framework. You should now have at least an idea of how to choose a web framework for your own server-side development. If not, then don't worry — later on in the course we'll give you detailed tutorials on Django and Express to give you some experience of actually working with a web framework.
230 Website security Beginner, CodingScripting, Guide, Intro, Learn, Security, Server-side programming, Web security, Website Security
This article has explained the concept of web security and some of the more common threats against which your website should attempt to protect. Most importantly, you should understand that a web application cannot trust any data from the web browser. All user data should be sanitized before it is displayed, or used in SQL queries and file system calls.
231 Tools and testing Accessibility, Automation, Beginner, CSS, CodingScripting, HTML, JavaScript, Landing, Learn, Testing, Tools, Topic, cross browser, user testing
Once you've started to become comfortable programming with core web technologies (like HTML, CSS, and JavaScript), and you start to get more experience, read more resources, and learn more tips and tricks, you'll start to come across all kind of tools, from ready-rolled CSS and JavaScript, to testing and automation apps, and more besides. As your web projects become larger and more complex, you'll want to start taking advantage of some of these tools, and working out reliable testing plans for your code. This part of the learning area aims to give you what you need get started and make informed choices.
232 Cross browser testing Accessibility, Automation, Beginner, CSS, CodingScripting, HTML, JavaScript, Landing, Learn, Module, Testing, Tools, cross browser
This module focuses on testing web projects across different browsers. We look at identifying your target audience (e.g. what users, browsers, and devices do you most need to worry about?), how to go about doing testing, the main issues that you'll face with different types of code and how to mitigate them, what tools are most useful in helping you test and fix problems, and how to use automation to speed up testing.
233 Handling common HTML and CSS problems Article, Beginner, CSS, CodingScripting, HTML, Learn, Selectors, Testing, cross browser, linting
Now you should be familiar with the main types of cross browser HTML and CSS problems that you'll meet in web development, and how to go about fixing them.
234 Handling common JavaScript problems Article, Beginner, CodingScripting, JavaScript, Learn, Libraries, Testing, cross browser, feature detection, linting, polyfills
So that's JavaScript. Simple huh? Maybe not so simple, but this article should at least give you a start, and some ideas on how to tackle the JavaScript-related problems you will come across.
235 Handling common accessibility problems Accessibility, Article, Beginner, CSS, CodingScripting, HTML, JavaScript, Learn, Testing, Tools, cross browser, keyboard
Hopefully this article has given you a good grounding in the main accessibility problems you might encounter, and how to test and overcome them.
236 Implementing feature detection Article, Beginner, CSS, CodingScripting, JavaScript, Learn, Modernizr, Testing, Tools, cross browser, feature detection
This article covered feature detection in a reasonable amount of detail, going through the main concepts and showing you how to both implement your own feature detection tests and use the Modernizr library to implement tests more easily.
237 Introduction to automated testing Article, Automation, Beginner, CodingScripting, Learn, Sauce Labs, Testing, Tools, Web Stack, cross browser
This was quite a ride, but I'm sure you can start to see the benefit in having automation tools do a lot of the heavy lifting for you in terms of testing.
238 Introduction to cross browser testing Article, Beginner, CodingScripting, Learn, Testing, concepts, cross browser
This article should have given you a high-level understanding of the most important concepts you need to know about cross browser testing. Armed with this knowledge, you are now ready to move on and start learning about Cross browser testing strategies.
239 Setting up your own test automation environment Article, Automation, Beginner, Browser, CodingScripting, Learn, Testing, Tools, cross browser, selenium
This module should have proven fun, and should have given you enough of an insight into writing and running automated tests for you to get going with writing your own automated tests.
240 Strategies for carrying out testing Article, Automation, Beginner, CodingScripting, Learn, Testing, concepts, cross browser, device lab, user testing, virtual machine
After reading this article you should now have a good idea of what you can do to identify your target audience/target browser list, and then effectively carry out cross browser testing on that list.
241 Web performance CSS, HTML, HTTP, JavaScript, Learn, Performance, Web Performance
Building websites requires HTML, CSS, and JavaScript. To build websites and applications people want to use, which attract and retain users, you need to create a good user experience. Part of good user experience is ensuring the content is quick to load and responsive to user interaction. This is known as web performance, and in this module you'll learn all you need to build performant websites.
242 CSS performance optimization CSS, Performance, Reference, Tutorial
Painting an unstyled page, and then repainting it once styles are parsed would be bad user experience. For this reason, CSS is render blocking, unless the browser knows the CSS is not currently needed. The browser can paint the page once it has downloaded the CSS and built the CSS object model. Browsers follow a specific rendering path: paint only occurs after layout, which occurs after the render tree is created, with requires both the DOM and the CSSOM trees. To optimize the CSSOM construction, remove unnecessary styles, minify, compress and cache it, and split CSS not required at page load into additional files to reduce CSS render blocking.
243 HTML Performance Features HTML, Learning, Web Performance
HTML is by default fast and accessible. It is our job, as developers, to ensure we don't break these two features.
244 Lazy loading Performance, Web Performance
Lazy loading is a stretegic delay of loading some assets until they are needed, usually based on user activity or navigation.
245 Multimedia: Images and Video Images, Media, Performance, Video, Web Performance
Media, namely images and video, account for over 70% of the bytes downloaded for the average website. In terms of download performance, eliminating media and reducing file size is the low hanging fruit. In this article, we look at optimizing image and video to imporvie web performance.
246 Perceived performance Perceived Performance, Web Performance
Perceived performance is how fast a website seems to the user. This article explores how users perceive performance and what can be done to improve perceived performance.
247 Recommended Web Performance Timings: How long is too long Performance, Reference, Tutorial, Web Performance
There is no clear set rules as to what constitutes a slow page, but there are specific guidelines for indicating content will load (1 second), idling (50ms), animating (16.7s) and responding to user input (50 to 200ms).
248 Understanding latency Web Performance
This article explains what latency is, how it impacts performance, how to measure latency, and how to reduce it.
249 Web performance basics
There are many reasons why your website should perform as well as possible.
Below is a concise introduction to best practices, tools, APIs and links to provide more information about each topic. It is also crucial to realize what is really important to your users. It might not be absolute timing, but user perception.
250 What is web performance Performance, Reference, Tutorial, Web Performance
Web performance is the objective time from when a request for content is made until the requested content is displayed in the user's browser and the subjective user experience of load time and runtime. Objectively, it is measurable time, in milliseconds, it takes for the web page or web application to be downloaded, painted in the user's web browser, and become responsive and interactive. Subjectively, it is the user's perception of whether content feels slow or fast it takes between the time the user requests the content and the time until the user feels the content requested is available and usable.
251 dns-prefetch Web Performance, dns-prefetch
When a browser requests a resource from a cross-origin (third party) server, that cross-origin’s domain name must be resolved to an IP address before the browser can issue the request. This process is known as DNS resolution. While many redundant layers of DNS caching can help to reduce this latency as much as possible, DNS resolution can add significant latency to requests. For websites that open connections to many third parties, this latency can significantly delay loading performance.

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