by 4 contributors:

Found 316 pages:

# Page Tags and summary
1 Glossary Beginner, Glossary, Index, Landing, beginner, glossary
Web technologies contain long lists of jargon and abbreviations that are used in documentation and coding. This glossary provides definitions of words and abbreviations you need to know to successfully understand and build for the web.
2 404 Glossary, HTTP Errors, Infrastructure, Navigation
A 404 is a Standard Response Code meaning that the server cannot find the requested resource.
3 502 502, Bad Gateway, Glossary, HTTP Errors, Infrastructure, Navigation
An HTTP error code meaning "Bad Gateway".
4 AJAX CodingScripting, Glossary, Infrastructure, glossary
AJAX (Asynchronous JavaScript And XML) is a programming practice of combining HTML, CSS, JavaScript, the DOM, and the XMLHttpRequest object to build complex webpages that update dynamically without entirely reloading.
5 API CodingScripting, Glossary, Infrastructure
An API (Application Programming Interface) is a set of features and rules allowing interaction between the software providing the API and other software components. In Web development, API commonly means a set of standard methods, properties, events, and URLs for interacting with Web content.
6 ARIA Accessibility, DesignAccessibility
ARIA (Accessible Rich Internet Applications) is a W3C specification for adding semantics and other metadata to HTML to cater to users of assistive technology.
7 ARPA Glossary, Infrastructure
.arpa (address and routing parameter area) is a top-level domain used for Internet infrastructure purposes, especially reverse DNS lookup (i.e., find the domain name for a given IP address).
8 ATAG ATAG, Authoring Tool Accessibility Guidelines, DesignAccessibility, Glossary
ATAG (Authoring Tool Accessibility Guidelines) is a W3C recommendation for building accessible-authoring tools that produce accessible contents.
9 Abstraction Abstraction, Coding, CodingScripting, Glossary, Programming Language
Abstraction in computer programming is a way to reduce complexity and allow efficient design and implementation in complex software systems. It hides the technical complexity of systems behind simpler APIs.
10 Accessibility Accessibility, DesignAccessibility, Glossary
Web Accessibility (A11Y) refers to best practices for keeping a website usable despite physical and technical restrictions. Web accessibility is formally defined and discussed at the W3C through the Web Accessibility Initiative (WAI).
11 Adobe Flash CodingScripting, Flash, Glossary, Infrastructure
Technical review completed.
12 Algorithm CodingScripting, Glossary
An algorithm is a self-contained series of instructions that perform a function.
13 Apple Safari Glossary, Navigation, WebMechanics
Safari is a Web browser developed by Apple and bundled with both OS X and iOS.
14 Argument CodingScripting, Glossary, JavaScript
An argument is a value (primitive or object) passed as input to a function.
15 Arpanet Glossary, Infrastructure
The ARPAnet (advanced research projects agency network) was an early computer network, constructed in 1969 as a robust medium to transmit sensitive military data and to connect leading research groups throughout the United States. ARPAnet first ran NCP (network control protocol) and subsequently the first version of the Internet protocol or TCP/IP suite, making ARPAnet a prominent part of the nascent Internet. ARPAnet was closed in early 1990.
16 Array Array, CodingScripting, Glossary, JavaScript, programming
An array is an ordered collection of data (either primitive or object). Based on its place in the array, each data item has a numeric index through which you can access the corresponding value. In JavaScript, arrays are also objects that can be manipulated with various methods.
17 Asynchronous Glossary, Web, WebMechanics
Technical review completed. Editorial review completed.
18 Attribute CodingScripting, Glossary, HTML
An attribute extends a tag, changing tag behavior or providing metadata. An attribute always has the form name=value (giving the attribute's identifier and the attribute's associated value).
19 Bandwidth Glossary, Infrastructure
Bandwidth is the measure of how much information can pass through a data connection in a given amount of time. It is usually measured in multiples of bits-per-second (bps), for example megabits-per-second (Mbps) or gigabits-per-second (Gbps).
20 BiDi DesignAccessibility, Glossary
BiDi (BiDirectional) refers to a document containing both right-to-left and left-to-right text. Even when both directionalities occur in the same paragraph, the text in each language must appear in its proper directionality.
21 Blink Glossary, Infrastructure, Layout
Blink is an open-source browser layout engine developed by Google as part of Chromium (and therefore part of Chrome as well). Specifically, Blink is a fork of the WebCore library in WebKit, which handles layout, rendering, and DOM.
22 Block Disambiguation, Glossary
The term block can have several meanings depending on the context. It may refer to:
23 Block (CSS) CSS, CodingScripting, DesignAccessibility, Glossary, HTML
block on a webpage is an HTML element that appears underneath the preceding element and above the following element. For example, <p> is by default a block-level element, whereas <a> is not (i.e., by default you can put a link in the middle of a paragraph; the link doesn't have to start its own line). Using display you can change whether an element displays inline or as a block (among many other options).
24 Block (scripting) CodingScripting, Glossary, JavaScript
In JavaScript, a block is a collection of related statements enclosed in braces ("{}"). For example, after if (condition) you can put a block of statements, indicating that the interpreter must skip the whole block if the condition is false.
25 Boolean CodingScripting, Glossary, JavaScript, Programming Languages, data types
In computer science, a boolean is a logical data type that can have only the values true or false.
26 Boot2Gecko B2G, Boot2Gecko, Firefox OS, Glossary, Infrastructure, Intro
Boot2Gecko (B2G) is the engineering codename for Firefox OS and refers to builds that haven't yet received official Firefox OS branding. (Firefox OS was also often called Boot2Gecko before the project had an official name.)
27 Browser Glossary, Navigation
A Web browser is a program that retrieves and displays pages from the Web, and lets users access further pages through hyperlinks.
28 Browsing context CodingScripting, Glossary
A browsing context is the environment in which a browser displays a Document (normally a tab nowadays, but possibly also a window or a frame within a page).
29 CDN Glossary, Infrastructure
CDN (Content Delivery Network) is a group of servers spread out over many locations. These servers store duplicate copies of data so that servers can fulfill data requests based on which servers are closest to the respective end-users. CDNs make for fast service less affected by high traffic.
30 CIA Glossary, Security, glossary
CIA (Confidentiality, Integrity, Availability) (also called the CIA triad or AIC triad) is a model that guides an organization's policies for information security.
31 CMS CMS, Composing, Content management system, Glossary, glossary
A CMS (Content Management System) is software that allows users to publish, organize, change, or remove various kinds of content, not only text but also embedded images, video, audio, and interactive code.
32 CORS Glossary, Infrastructure, Security, glossary
It is insecure to allow a webpage to request any resources from any other domains without limitation. CORS (Cross-Origin Resource Sharing) is a system that determines whether to block or fulfill these requests.
33 CRUD Glossary, Infrastructure, glossary
CRUD (Create, Read, Update, Delete) is an acronym for ways one can operate on stored data. It is a mnemonic for the four basic functions of persistent storage.  CRUD typically refers to operations performed in a database or datastore, but it can also apply to higher level functions of an application such as soft deletes where data is not actually deleted but marked as deleted via a status.
34 CSP Glossary, HTTP, Infrastructure, glossary
A CSP (Content Security Policy) is used to detect and mitigate certain types of website related attacks like XSS and data injections.
35 CSRF Glossary, Security
CSRF (Cross-Site Request Forgery) is an attack that impersonates a trusted user and sends a website unwanted commands. This can be done, for example, by including malicious parameters in a URL behind a link that purports to go somewhere else.
36 CSS CSS, CodingScripting, Glossary
CSS (Cascading StyleSheets) is a declarative language that controls how webpages look in the browser. The browser applies CSS style declarations to selected elements to display them properly. A style declaration contains the properties, with their values, that determine how a webpage looks.
37 CSS Selector CSS, CSS Selector, CodingScripting, Glossary, HTML, Selector
CSS selector is a pattern rule that matches style rules to a specific element (or elements). The selector begins a rule set and precedes definitions of how the element(s) should look.
38 CalDAV CalDAV, Glossary, Infrastructure
CalDAV (Calendaring extensions to WebDAV) is a protocol standardized by the IETF and used to remotely access calendar data from a server.
39 Call stack CodingScripting, Glossary
call stack is a mechanism for an interpreter to keep track of its place in a script that calls functions from within functions.
40 Canvas CodingScripting, Glossary, Graphics, HTML, JavaScript
The HTML <canvas> element provides an empty graphic zone on which specific JavaScript APIs can draw (such as Canvas 2D or WebGL).
41 CardDAV CardDAV, Glossary, Infrastructure
CardDAV (vCard Extension to WebDAV) is a protocol standardized by the IETF and used to remote-access or share contact information over a server.
42 Certificate authority Cryptography, Glossary, Security
A certificate authority (CA) is an organization that signs digital certificates and their associated public keys. This certifies that an organization that requested a digital certificate (e.g., Mozilla Corporation) is authorized to request a certificate for the subject named in the certificate (e.g.,
43 Certified Apps, B2G, Firefox OS, Glossary, Security, Trustworthy, glossary
Certified means that an application, content or data transmission has successfully undergone evaluation by professionals with expertise in the relevant field, thereby indicating completeness, security and trustworthiness.
44 Character CodingScripting, Glossary, strings
A character is either a symbol (letters, numbers, punctuation) or non-printing "control" (e.g., carriage return or soft hyphen).  UTF-8 is the most common character set and includes the graphemes of the most popular human languages.
45 Chrome Browser, Chrome, Glossary, WebMechanics
Not to be confused with Google Chrome, chrome is any visible aspect of a browser aside from the webpages themselves (e.g., toolbars, menu bar, tabs).
46 Cipher Cryptography, Glossary, Privacy, Security
In cryptography, a cipher is an algorithm that can encode cleartext to make it unreadable, and to decode it back.
47 Cipher suite Cryptography, Glossary, Security
A cipher suite is a combination of a key exchange algorithm, authentication method, bulk encryption cipher, and message authentication code.
48 Ciphertext Cryptography, Glossary, Privacy, Security
In cryptography, a ciphertext is a scrambled message that conveys information but is not legible unless decrypted with the right cipher and the right secret (usually a key), reproducing the original cleartext. A ciphertext's security, and therefore the secrecy of the contained information, depends on using a secure cipher and keeping the key secret.
49 Class CodingScripting, Glossary
In object-oriented programming, a class defines an object's characteristics. Class is a template definition of an object's properties and methods, the "blueprint" from which other more specific instances of the object are drawn.
50 Closure CodingScripting, Glossary, glossary
The binding which defines the scope of execution. In JavaScript, functions create a closure context.
51 Codec Glossary, WebMechanics, glossary
A codec  (a derivative from "coder-decoder") is a computer program that encodes or decodes a data stream.
52 Compile CodingScripting, Glossary, glossary
Compiling is the process of transforming a computer program in a given programming language into the same program written in another language (normally a binary language that the computer can execute).
53 Compile time CodingScripting, Glossary, JavaScript, glossary
The compile time is the time from when the program is first loaded until the program is parsed.
54 Computer Programming CodingScripting, Computer Programming, Programming Language, programming
Programming is a process that formulates the solution of a computing problem, or automates a repetitive task, as a series of sequential instructions in an executable program.
55 Constant CodingScripting, Constant, Glossary, glossary
A constant is a value that the programmer cannot change, for example numbers (1, 2, 42). With variables, on the other hand, the programmer can assign a new value to a variable name already in use.
56 Constructor CodingScripting, Glossary, glossary
A constructor belongs to a particular class object that is instantiated. The constructor initializes this object and can provide access to its private information. The concept of a constructor can be applied to most object-oriented programming languages. Essentially, a constructor in JavaScript is usually declared at the instance of a class.
57 Control flow CodingScripting, Glossary, JavaScript, glossary
The control flow is the order in which the computer executes statements in a script.
58 Copyleft Glossary, OpenPractices, Remixing, Sharing, glossary
Copyleft is a term, usually referring to a license, used to indicate that such license requires that redistribution of said work is subject to the same license as the original. Examples of copyleft licenses are the GNU GPL (for software) and the Creative Commons SA (Share Alike) licenses (for works of art).
59 Crawler Browser, Crawler, Glossary, Infrastructure, glossary
A web crawler is a program, often called a bot or robot, which systematically browses the Web to collect data from webpages.  Typically search engines use crawlers to build indexes.
60 Cross-site scripting Cross Site Scripting, DOM, Glossary, Security, XSS, glossary
Cross-site scripting (XSS) is a security exploit which allows an attacker to inject into a website malicious client-side code. This code is executed by the victims and lets the attackers bypass access controls and impersonate users. According to the Open Web Application Security Project, XSS was the third most common Web app vulnerability in 2013.
61 Cryptanalysis Cryptography, Glossary, Privacy, Security, glossary
Cryptanalysis is the branch of cryptography that studies how to break codes and cryptosystems. Cryptanalysis creates techniques to break ciphers, in particular by methods more efficient than a brute-force search. In addition to traditional methods like frequency analysis and index of coincidence, cryptanalysis includes more recent methods, like linear cryptanalysis or differential cryptanalysis, that can break more advanced ciphers.
62 Cryptographic hash function Cryptography, Glossary, Security
A cryptographic hash function is a cryptographic primitive transforming a message of arbitrary size into a message of fixed size, called a digest. Cryptographic hash functions are used for authentication, digital signatures, and message authentication codes.
63 Cryptography Cryptography, Glossary, Privacy, Security, glossary
Cryptography, or cryptology, is the science that studies how to encode and transmit messages securely. Cryptography designs and studies algorithms used to encode and decode messages in an insecure environment, and their applications.
64 DHTML CodingScripting, DHTML, Glossary, HTML
DHTML (Dynamic HTML) refers to the code behind interactive webpages that need no plugins like Flash or Java. DHTML aggregates the combined functionality of HTML, CSS, the DOM, and JavaScript.
65 DNS DNS, Domain Name System, Glossary, Infrastructure
DNS (Domain Name System) translates easy-to-recall domain names to the numerical IP addresses needed to find a particular computer service on the Internet or private network.
66 DOM CodingScripting, DOM, Glossary
The DOM (Document Object Model) is an API that represents and interacts with any HTML or XML document. The DOM is a document model loaded in the browser and representing the document as a node tree, where each node represents part of the document (e.g. an element, text string, or comment).
67 DTD CodingScripting, Glossary
<!DOCTYPE> informs the browser which version of HTML (or XML) you used to write the document. Doctype is a declaration, not a tag; you can also refer to it as "document type declaration", or "DTD" for short.
68 Decryption Cryptography, Glossary, Privacy, Security
In cryptography, decryption is the conversion of ciphertext into cleartext.
69 Denial of Service Attack, Denial of Service, Glossary, Intro, Security
DOS (Denial of service) is an attack on computers or networks that restricts or prevents legitimate use. In a DOS attack, an attacker uses a flood of packets to slow down or crash the target system or an entire network.
70 Digest Cryptography, Glossary, Privacy, Security
digest is a small value generated by a hash function from a whole message. Ideally, a digest is quick to calculate, irreversible, and unpredictable, and therefore indicates whether someone has tampered with a given message.
71 Digital certificate Cryptography, Glossary, Security
A digital certificate is a data file that binds a publicly known cryptographic key to an organization. A digital certificate contains information about an organization, such as the common name (e.g.,, the organization unit (e.g., Mozilla Corporation), and the location (e.g., Mountain View). Digital certificates are most commonly signed by a certificate authority, attesting to the certificate's authenticity.
72 Distributed Denial of Service Attack, DDoS, Denial of Service, Glossary, Intro, Security
A Distributed Denial-of-Dervice (DDoS) is an attack in which many compromised systems are made to attack a single target, in order to swamp server resources and block legitimate users.
73 DoS attack Glossary, Security
DoS (Denial of Service) is a network attack that prevents legitimate use of server resources by flooding the server with requests.
74 Doctype Browser, CodingScripting, DOCTYPE, Glossary, HTML, Intro
<!DOCTYPE> informs the browser which version of HTML (or XML) you used to write the document. Doctype is a declaration, not a tag; you can also refer to it as "document type declaration", or "DTD" for short.
75 Domain Browser, Domain, Infrastructure, Networking
A domain is the part of a computer network in which one entity controls the data processing resources, for example a website.
76 Domain name Domain Name, Glossary, Protocol, WebMechanics
A domain name is a website's address on the Internet. Domain names are used in URLs to identify to which server belong a specific webpage. The domain name consists of a hierarchial sequence of names (labels) separated by periods (dots) and ending with an extension.
77 Dynamic typing CodingScripting, Glossary, ProgrammingLanguage
Dynamically-typed languages are those (like JavaScript) where the interpreter assigns variables a type at runtime based on the variable's value at the time.
78 ECMA Glossary, Stub, WebMechanics, l10n:priority
Ecma International (formally European Computer Manufacturers Association) is a non-profit organization that develops standards in computer hardware, communications, and programming languages.
79 ECMAScript Glossary, WebMechanics, glossary
No summary!
80 Element CodingScripting, Glossary, HTML
An element is a part of a webpage. In XML and HTML, an element may contain a data item or a chunk of text or an image, or perhaps nothing. A typical element includes an opening tag, attributes, content, and a closing tag:
81 Empty element CodingScripting, Glossary, Intermediate, glossary
An empty element is an element from HTML, SVG, or MathML that cannot have any child nodes (i.e., nested element or text inside an element).
82 Encapsulation CodingScripting, Glossary
Encapsulation is the packing of data and functions into one component (for example, a class) and then controlling access to that component to make a "blackbox" out of the object. Because of this, a user of that class only needs to know its interface (that is, the data and functions exposed outside the class), not the hidden implementation.
83 Encryption Cryptography, Glossary, Privacy, Security
In cryptography, encryption is the conversion of cleartext into a coded text or ciphertext. A ciphertext is intended to be unreadable by unauthorized readers.
84 Endianness Coding, CodingScripting, Glossary, glossary
"Endian" and "endianness" (or "byte-order") describe how computers organize the bytes that make up numbers.
85 Engine CodingScripting, Glossary, NeedsContent, glossary
The JavaScript engine is an interpreter that parses and executes a JavaScript program.
86 Entity CodingScripting, Composing, Glossary, HTML
In HTML, every character can be represented by a string that begins with & and is called an entity. You must use entities instead of restricted characters if you don't want the character interpreted as markup. For example, if you want a greater-than sign (">") for some use besides closing a tag, you must write &gt; instead.
87 Exception Beginner, CodingScripting, Glossary, beginner, glossary
An exception is a condition that interrupts normal code execution. In JavaScript syntax errors are a very common source of exceptions.
88 Expando CodingScripting, JavaScript, Reference, Réference, Référence, expando
Expando properties are properties added to DOM nodes with JavaScript but not part of the object's DOM specification:
89 FTP CodingScripting, FTP, Glossary, Protocol
FTP (File Transfer Protocol) is the standard network protocol for transferring files from one host to another over the Internet through TCP.
90 FTU Collaborating, DesignAccessibility, FTU, Firefox OS, First time use, Gaia, Glossary, Intro
FTU (First Time Use) is the app that loads when you run a newly-installed version of Gecko on a Firefox OS device.
91 Falsy CodingScripting, Glossary, JavaScript
A falsy value is a value that translates to false when evaluated in a Boolean context.
92 Firefox OS B2G, Boot2Gecko, Firefox OS, Glossary, Infrastructure, Intro
Firefox OS is Mozilla's mobile operating system, based on Linux and Firefox's powerful Gecko rendering engine. Firefox OS consists mainly of Gaia, Gecko, and Gonk.
93 Forbidden header name Fetch, Glossary, HTTP, forbidden, headers
A forbidden header name is an HTTP header name that cannot be modified programmatically.
94 Forbidden response header name Glossary, HTTP, Response, forbidden, headers
A forbidden response header name is an HTTP header name (either `Set-Cookie` or `Set-Cookie2`) that cannot be modified programmatically.
95 Function CodingScripting, Glossary, JavaScript
A function is a code snippet that can be called by other code or by itself, or a variable that refers to the function. When a function is called, arguments are passed to the function as input, and the function can optionally return an output. A function in JavaScript is also an object.
96 GIF Composing, Glossary, glossary
GIF (Graphics Interchange Format) is an image format that allows lossy compression of images and can be used for animations. To achieve compression, it uses up to 8 bit per pixel, allowing use of 256 colors out of the 24-bits color space.
97 GIJ
Gaia integration Testing. Marionette- and JavaScript- based. See GIJ.
98 GPL GPL, Glossary, License, OpenPractices, Remixing, Sharing
The (GNU) GPL (General Public License) is a copyleft free software license published by the Free Software Foundation. Users of a GPL-licensed program are granted the freedom to use it, read the source code, modify it and redistribute the changes they made, provided they redistribute the program (modified or unmodified) under the same license.
99 Gaia B2G, Boot2Gecko, Firefox OS, Gaia, Glossary, Infrastructure, Intro
The user interface and default application suite of the Firefox OS platform.
100 Gecko Firefox OS, Gecko, Glossary, Infrastructure, Intro, Mozilla
Gecko is the layout engine developed by the Mozilla Project and used in many apps/devices, including Firefox and Firefox OS.
101 Git Collaborating, Glossary
Git is a free, open-source, distributed Source Code Management (SCM) system. It facilitates handling code bases with distributed develompent teams. What sets it apart from previous SCM systems is the ability to do common operations (branching, committing, etc.) on your local development machine, without having to change the master repository or even having write access to it.
102 Global attribute Attribute, CodingScripting, Glossary, HTML
Global attributes are attributes that can be used on all elements (though sometimes without effect on some elements).
103 Global object CodingScripting, Glossary, NeedsContent
An object that always exists in the global scope.  In most interpreters, this is the window host object.
104 Global scope CodingScripting, Glossary, NeedsContent
The scope that is visible in all other scopes.
105 Global variable CodingScripting, Glossary
A global variable is a  variable that is declared in the global scope in other words, a variable that is visible from all other scopes. In JavaScript it is a property of the global object.
106 Gonk B2G, Boot2Gecko, Firefox OS, Glossary, Gonk, Infrastructure, Intro
Gonk is the lower-level operating system of Firefox OS and consists of a Linux kernel (based on the Android Open Source Project (AOSP)) and userspace hardware abstraction layer (HAL).
107 Google Chrome Browser, Chrome canary, Chrome stable, Chromium, Glossary, WebMechanics, google chrome
Google Chrome is a free Web browser developed by Google. It's based on the Chromium open source project. Some key differences are described on the Chromium wiki. For a layout engine, both browsers use a fork of WebKit called Blink.
108 Guard API, CodingScripting, Glossary, guard
Guard is a feature of Headers objects (as defined in the Fetch spec, which affects whether methods such as set() and append() can change the header's contents. For example, immutable guard means that headers can't be changed. For more information, read Fetch basic concepts: guard.
109 HTML CodingScripting, Glossary, HTML
HTML (HyperText Markup Language) is a descriptive language that specifies webpage structure.
110 HTML5 CodingScripting, Glossary, HTML, HTML5, MarkUp
The latest stable release of HTML, HTML5 takes HTML from a simple markup for structuring a document to a full app development platform. Among other features, HTML5 includes new elements and JavaScript APIs to enhance storage, multimedia, and hardware access.
111 HTTP Beginner, Glossary, HTTP, Infrastructure
HTTP (HyperText Transfer Protocol) is the basic protocol that enables file transfer on the Web. HTTP is textual (all communication is done in plain text) and stateless (no communication is aware of previous communications).
112 Hoisting CodingScripting, Glossary, JavaScript
In JavaScript, functions and variables are hoisted. Hoisting is JavaScript's behavior of moving declarations to the top of a scope (the global scope or the current function scope).
113 Host Glossary, Intermediate, Web, WebMechanics
A host is a device connected to the Internet (or a local network). Some hosts called servers offer additional services like serving webpages or storing files and emails.
114 Hotlink Glossary, WebMechanics
A hotlink (also known as inline link) is an object (typically an image) directly linked to another object on another site. For example, an image hosted on is shown directly on
115 Hyperlink CodingScripting, Glossary, HTML, Navigation
Hyperlinks connect webpages or data items to one another. In HTML, <a> elements define hyperlinks from a spot on a webpage (like a text string or image) to another spot on some webpage (even the same page).
116 Hypertext Glossary, Web, WebMechanics
Hypertext is text that contains links to other texts, as opposed to a single linear flow like in a novel.
117 I18N Beginner, Credibility, Glossary, Internationalization, OpenPractices, i18n
i18n (from "internationalization", a 20-letter word) is the best practice that enables products or services to be readily adapted to any target culture.
118 IANA Glossary, Infrastructure
IANA (Internet Assigned Numbers Authority) is a subsidiary of ICANN charged with recording and/or assigning domain names, IP addresses, and other names and numbers used by Internet protocols.
119 ICANN Glossary, Infrastructure
ICANN (Internet Corporation of Assigned Names and Numbers) is an international nonprofit that maintains the domain name system and the record of IP addresses.
120 ICE CodingScripting, Glossary
ICE (Interactive Connectivity Establishment) is a framework used by WebRTC for connecting two peers to each other, regardless of network topology (usually for audio- or videochat).
121 IDE CodingScripting, Glossary
An Integrated Development Environment (IDE) or Interactive Development environment is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of a source code editor, build automation tools and a debugger.
122 IDL CodingScripting, Glossary, IDL, Interface description language
An IDL (Interface Description Language) is a generic language used to specified objects' interfaces apart from any specific programming language.
123 IETF Glossary, IETF, Infrastructure, Internet
The Internet Engineering Task Force (IETF) is a worldwide organization that drafts specifications governing the mechanisms behind the Internet, especially the TCP/IP or Internet Protocol Suite. The IETF is open, run by volunteers, and sponsored by the Internet Society.
124 IIFE CodingScripting, Glossary, JavaScript
IIFE (Immediately Invoked Function Expression) is a JavaScript function executed as soon as it is defined.
125 IMAP Beginner, Glossary, Infrastructure, MailNews
IMAP (Internet Message Access Protocol) is a protocol used to retrieve and store emails. More recent than POP3, IMAP allows folders and rules on the server.
126 IP Address Beginner, Glossary, Infrastructure, Web
An IP address is a number assigned to every device connected to a network that uses the Internet protocol.
127 IPv4 Glossary, IPv4, Infrastructure, Internet Protocol, Protocol
IPv4 is the fourth version of the communication protocol underlying the Internet and the first version to be widely deployed.
128 IPv6 Glossary, IPv6, Infrastructure, Intermediate, Web, WebMechanics
IPv6 is the current version of the communication protocol underlying the Internet. Slowly IPv6 is replacing IPv4, among other reasons because IPv6 allows for many different IP addresses.
129 IRC Glossary, Infrastructure, Internet Relay Chat, Open Protocol, irc
IRC (Internet Relay Chat) is a worldwide chat system requiring an Internet connection and an IRC client, which sends and receives messages via the IRC server.
130 ISO Glossary, ISO, Infrastructure, Web Standards, web specifications
Technical review completed. Editorial review completed.
131 ISP Glossary, ISP, Internet Service Provider, Web, WebMechanics
An ISP (Internet Service Provider) sells Internet access, and sometimes email, web hosting, and voice over IP, either by a dial-up connection over a phone line (formerly more common), or through a broadband connection such as a cable modem or DSL service.
132 Identifier Beginner, Glossary, Sharing
A sequence of characters in the code that identifies a variable, function, or property.
133 Immutable CodingScripting, Glossary
An immutable object is one whose content cannot be changed.
An object can be immutable for various reasons, for example:
134 Index Glossary, Index, MDN, Navigation, meta
Found 316 pages:
135 IndexedDB API, CodingScripting, Glossary, l10n:priority
IndexedDB is a Web API for storing large data structures within browsers and indexing them for high-performance searching. Like an SQL-based RDBMS, IndexedDB is a transactional database system. However, it uses JavaScript objects rather than fixed columns tables to store data.
136 Inheritance CodingScripting, Glossary, Inheritance, Programming Language
Inheritance is a major feature of object-oriented programming.  Data abstraction can be carried up several levels, that is, classes can have superclasses and subclasses.
137 Instance Beginner, CodingScripting, Glossary, JavaScript, NeedsContent
An object created by a constructor is an instance of that constructor.
138 Internationalization Beginner, DesignAccessibility, Glossary, Internationalization, OpenPractices, i18n
i18n (from "internationalization", a 20-letter word) is the best practice that enables products or services to be readily adapted to any target culture.
139 Internet Beginner, Glossary, Guide, Intro, NeedsContent, Tutorial, Web, WebMechanics
The Internet is a worldwide network of networks that uses the Internet protocol suite (also named TCP/IP from its two most important protocols).
140 JPEG Beginner, Composing, Glossary, JPEG, beginner
JPEG an acronym for the Joint Photographic Experts Group.  A commonly used method of lossy compression for digital images.
141 JSON CodingScripting, Glossary, Intro, JSON
The JavaScript Object Notation (JSON) is a data-interchange format.  Although not a strict subset, JSON closely resembles a subset of JavaScript syntax. Though many programming languages support JSON, JSON is especially useful for JavaScript-based apps, including websites and browser extensions.
142 Jank Beginner, CodingScripting, Glossary, Performance
Jank refers to sluggishness in a user interface, usually caused by executing long tasks on the main thread, blocking rendering, or expending too much processor power on background processes.
143 Java CodingScripting, Glossary, Java, Programming Language
Java is an object-oriented, class-based, portable  computer programming language designed for minimal implementation dependencies.
144 JavaScript CodingScripting, Glossary, JavaScript
JavaScript (JS) is a programming language mostly used client-side to dynamically script webpages, but often also server-side.
145 Key Cryptography, Glossary, Security
A key is a piece of information used by a cipher for encryption and/or decryption. Encrypted messages should remain secure even if everything about the cryptosystem, except for the key, is public knowledge.
146 Keyword Glossary, Keyword, Search, keyword search
A keyword is a word or phrase that describes content.  Online keywords are used as queries for search engines or as words identifying content on websites.
147 LGPL Glossary, License, OpenPractices, Remixing, Sharing
LGPL (GNU Lesser General Public License) is a free software license published by the Free Software Foundation. The LGPL provides a more permissive alternative for the strictly copyleft GPL. While any derivative work using a GPL-licensed program must be released under the same terms (free to use, share, study, and modify), the LGPL only requires the LGPL-licensed component of the derivative program to continue using the LGPL, not the whole program. LGPL is usually used to license shared components such as libraries (.dll, .so, .jar, etc.).
148 Ligature CSS, DesignAccessibility, Glossary
A ligature is a joining of two characters into one shape. For example, in French "œ" is a ligature of "oe".
149 Local scope CodingScripting, Glossary, NeedsContent
Local scope is a characteristic of variables that makes them local (i.e., the variable name is only bound to its value within a given function).
150 Local variable CodingScripting, Glossary, NeedsContent
A variable whose name is bound to its value only within a single function.
151 Locale Composing, Glossary, Locale
Locale is a set of language- or country-based preferences for a user interface.
152 Localization Collaborating, Glossary, Intro, Localization, WebMechanics
Localization (l10n) is the process of adapting a software user interface to a specific culture.
153 MIME type Glossary, WebMechanics
MIME type (now properly called "media type", but also sometimes "content type") is a string sent along with a file indicating the file type (for example, a sound file might be labeled audio/ogg, or an image file image/png). It serves the same purpose as filename extensions traditionally do on Windows.
154 MathML CodingScripting, Glossary, MathML, Mathematical Markup Language, XML
MathML (an XML application) is an open standard for representing mathematical expressions in webpages.  In 1998 the W3C first recommended MathML for representing mathematical expressions in the browser. MathML has other applications also including scientific content and voice synthesis.
155 Method CodingScripting, Glossary
A method is a function which is a property of an object. It exist two kind of methods: Instance Method which are built-in tasks performed by an object instance, or Static Methods which are tasks that can by performed without the need of an object instance.
156 Microsoft Edge Browser, Glossary, Infrastructure
Microsoft Edge is a free-of-cost graphical Web browser bundled with Microsoft Windows and developed by Microsoft since 2014. Initially known as Spartan, Edge replaced the longstanding Microsoft browser Internet Explorer.
157 Microsoft Internet Explorer Browser, Glossary, Internet Explorer, Microsoft, Microsoft Internet Explorer, Navigation, Web Browser, Windows, Windows Operating System
Internet Explorer (or IE) is a free graphical browser maintained by Microsoft.
158 Mixin CodingScripting, Glossary, Method, Property
A mixin is a coherent set of methods and properties implemented by other interfaces and classes. The properties and methods are then part of the new interface in the same way as any specific properties and methods.
159 Mobile First DesignAccessibility, Glossary
Mobile first, a development of progressive enhancement, is a design philosophy that values focused, mobile-ready websites over complex, demanding ones.
160 Modularity CodingScripting, Glossary
Modularity refers to the division of a software package into logical units. The advantage of a modular system is that it's easier to reason about parts of the software package independently.
161 Mozilla Firefox Browser, Firefox, Glossary, Infrastructure, Mozilla, Mozilla Firefox
Mozilla Firefox is a free open-source browser whose development is overseen by the Mozilla Corporation. Firefox runs on Windows, OS X, Linux, and Android.
162 Mutable CodingScripting, Glossary, NeedsContent, glossary
Mutable is a type of variable that can be changed. In JavaScript, only objects and arrays are mutable, not primitive values.
163 NAT Beginner, Glossary, Infrastructure, WebMechanics, WebRTC
NAT (Network Address Translation) is a technique for letting multiple computers share an IP address. NAT assigns unique addresses to each computer on the local network and adjusts incoming/outgoing network traffic to send data to the right place.
164 NNTP Glossary, Infrastructure, glossary
NNTP (Network News Transfer Protocol) is a protocol used to transfer Usenet messages from client to server or between servers.
165 NaN CodingScripting, Computing, Glossary, NaN, glossary
NaN (Not a Number) is a numeric data type that means an undefined value or value that cannot be represented, especially results of floating-point calculations.
166 Namespace CodingScripting, Glossary, Operating System, glossary
Namespace is a context for identifiers, a logical grouping of names used in a program. Within the same context and same scope,  an identifier must uniquely identify an entity.
167 Native CodingScripting, Glossary, glossary
A native application has been compiled to run on the hardware-software combination customary to the targeted architecture.
168 Netscape Navigator Browser, Glossary, Navigation, Netscape, Netscape Navigator, glossary, navigation
Netscape Navigator or Netscape was a leading browser in the 1990s.  Netscape was based on Mosaic and the Netscape team was led by Marc Andreessen, a programmer who also wrote code for Mosaic.
169 Node Disambiguation, Glossary, glossary
The term node can have several meanings depending on the context. It may refer to:
170 Node (DOM)
In the context of the DOM, a node is a single point in the node tree. Various things that are nodes are the document itself, elements, text, and comments.
171 Node (networking) Glossary, Infrastructure, glossary
In networking, a node is a single point in the network. In phisical networks, a node is usually a device, like a computer or a router.
172 Node.js Glossary, Infrastructure, JavaScript, glossary, l10n:priority, node.js
Node.js is a cross-platform JavaScript runtime environment that allows developers to build server-side and network applications with JavaScript.
173 Normative Glossary, Specification, Standardization, glossary
Normative is a word commonly used in software specifications to denote sections that are standardized and must be followed as a rule. Specifications might also contain sections that are marked as non-normative or informative, which means those are provided there for the purpose of helping the reader understand the specifications better or to showcase an example or a best pracice, which need not be followed as a rule.
174 Null CodingScripting, Glossary, glossary
In computer science, a null value represents a reference that points, generally intentionally, to a nonexistent or invalid object or address. The meaning of a null reference varies among language implementations.
175 Number CodingScripting, Glossary, JavaScript
In JavaScript, Number is a numeric data type in the double-precision 64-bit floating point format (IEEE 754). In other programming languages different numeric types can exist, for examples: Integers, Floats, Doubles, or Bignums.
176 OOP Beginner, CodingScripting, Glossary, beginner, glossary
OOP (Object-Oriented Programming) is an approach in programming in which data is encapsulated within objects and the object itself is operated on, rather than its component parts.
177 OTA Glossary, Infrastructure, Intro, OTA, Over the air, glossary, l10n:priority, updates
Over The Air (OTA) refers to automatic updating of software on connected devices from a central server. All device owners receiving a given set of updates are on the same "channel", and each device often can access several channels (e.g. for production or engineering builds).
178 OWASP Glossary, Security
OWASP (Open Web Application Security Project) is a non-profit organization and worldwide network that works for security in Free Software, especially on the Web.
179 Object CodingScripting, Glossary, Intro, Object, glossary
Object refers to a data structure containing data and instructions for working with the data. Objects sometimes refer to real-world things, for example a car or map object in a racing game. JavaScript, Java, C++, Python, and Ruby are examples of object-oriented programming languages.
180 Object reference CodingScripting, Glossary, glossary
A link to an object. Object references can be used exactly like the linked objects. The concept of object references arises when assigning the same object to more than one property. Rather than holding a copy of the object, each assigned property holds object references that link to the same object, so that when the object changes all properties referring to the object reflect the change.
181 OpenGL CodingScripting, Glossary, OpenGL, glossary
OpenGL (Open Graphics Library) is a cross-language, multi-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardware-accelerated rendering.
182 OpenSSL Glossary, Security, glossary
OpenSSL is an open-source implementation of SSL and TLS.
183 Opera Browser Browser, Glossary, Navigation, Opera, Opera Browser, glossary, navigation
Opera is the fifth most used web browser, publicly released in 1996 and initially running on Windows only. Opera uses Blink as its layout engine since 2013 (before that, Presto). Opera also exists in mobile and tablet versions.
184 Operand CodingScripting, Glossary, glossary
An operand is the part of an instruction representing the data manipulated by the operator. For example, when you add two numbers, the numbers are the operand and "+" is the operator.
185 Operator CodingScripting, Glossary, glossary
Reserved syntax consisting of punctuation or alphanumeric characters and carrying out built-in functionality.  For example, "+" indicates the addition operator and "!" indicates the "not" operator.
186 Origin Glossary, WebMechanics, origin
The origin of web content is defined by the scheme (protocol), host (domain), and port of the URL used to access it. Two objects have the same origin only when the scheme, host, and port match.
187 P2P Glossary, Infrastructure, Networking, P2P
P2P (Peer-to-peer) is a computer networking architecture in which all participating nodes (peers) have equal privileges and share the workload. P2P differs from a client-server network architecture, where multiple client nodes connect to centralized servers for services.
188 PDF Composing, Glossary, PDF, Portable Document Format, glossary
PDF (Portable Document Format) is a file format used to share documentation without depending on any particular software implementation, hardware platform, or operating system. PDF provides a digital image of a printed document, and keeps the same appearance when printed.
189 PHP CodingScripting, Glossary, Infrastructure, PHP, glossary
PHP is a server-side scripting language for building web apps and dynamic websites.
190 PNG Beginner, Glossary, PNG, beginner, glossary
PNG Portable Network Graphics supports lossless data compression and is a graphics file format.
191 POP3 Beginner, Glossary, Infrastructure, beginner, glossary
POP3 (Post Office Protocol) is a very common protocol for getting emails from a mail server over a glossary("TCP"} connection. POP3 does not support folders, unlike the more recent IMAP4, which is harder to implement because of its more complex structure.
192 Parameter CodingScripting, Glossary, JavaScript
A parameter is a named variable passed into a function. Parameter variables are used to import arguments into functions.
193 Parent object CodingScripting, Glossary, NeedsContent
The object to which a given property belongs.
194 Parse CodingScripting, Glossary, NeedsContent
To analyze and convert a program into an internal format that the JavaScript engine can handle efficiently. In JavaScript, this is done during compile time or whenever the parser is invoked, such as during a call to the eval method.
195 Parser CodingScripting, Glossary, NeedsContent
The module that parses.
196 Placeholder names Cryptography, Glossary, Security
Placeholder names are commonly used in cryptography to indicate the participants in a conversation, without resorting to terminology such as "Party A," "eavesdropper," and "malicious attacker."
197 Plaintext Cryptography, Glossary, Security
Plaintext refers to information that is being used as an input to an encryption algorithm, or to ciphertext that has been decrypted.
198 Polyfill CodingScripting, Glossary
A polyfill is a piece of code used to provide modern and expected functionalities on browsers that do not support them. For example it could be used to mimic the functionality of an HTML Canvas element on Microsoft Internet Explorer 7 (which didn't support that element) by using, for example, a Silverlight plugin.
199 Polymorphism CodingScripting, Glossary, glossary
Polymorphism is the presentation of one interface for multiple data types.

For example, integers, floats, and doubles are implicitly polymorphic: regardless of their different types, they can all be added, subtracted, multiplied, and so on.
200 Port Glossary, Intro, Security, computer network, glossary, l10n:priority, port
For a computer connected to a network with an IP address, a port is a communication endpoint. Ports are designated by numbers, and below 1024 each port is associated by default with a specific protocol.
201 Presto Glossary, Infrastructure, l10n:priority
Presto was the proprietary browser layout engine used to power the Opera browser until version 15. Since then, the Opera browser is based on Chromium, which uses the Blink layout engine.
202 Primitive CodingScripting, Glossary, JavaScript, glossary
A primitive (primitive value, primitive data type) is data that is not an object and has no methods.
203 Privileged Glossary, Security, glossary
Users are said to be privileged when they are granted additional rights to a system, or given ultimate access to content in a higher priority level when compared to normal users.
204 Progressive Enhancement DesignAccessibility, Glossary, glossary
Progressive enhancement is a design philosophy that delivers a first-class experience in restricted scenarios, serving up essential content and functionality to everyone and adding optional features as needed. It is more like a strategy and a plan in web-design which gives special importance to accessiblity and many scripting technologies. It is a very useful technique that allows Web developers to focus on developing the best possible websites while balancing the issues in those websites being accessed by multiple unknown user-agents.
205 Property Disambiguation, Glossary
The term property can have several meanings depending on the context. It may refer to:
206 Property (CSS) CodingScripting, Glossary
A CSS property is a characteristic (like color) whose associated value defines one aspect of how the browser should display the element.
207 Property (JavaScript) CodingScripting, Glossary, glossary
A property is a characteristic of an object, often describing attributes associated with a data structure. It exists to kind of properties: an Instance Property which holds data specific to a given object instance, or a Static Property which holds data shared between all object instances.
208 Protocol Glossary, Infrastructure, Protocols, glossary
A protocol is a system of rules that define how data is exchanged within or between computers.  Communications between devices require that the devices agree on the format of the data that is being exchanged. The set of rules that defines a format is called a protocol.
209 Prototype Apps, Composing, Glossary, glossary
A prototype is the development model which displays the apperance and behavior of an application or product to be built.
210 Pseudo-class CSS, CodingScripting, Glossary, Selector
In CSS, a pseudo-class selector targets elements depending on their state rather than on information from the document tree. For example, the selector a:visited applies styles only to links that the user has already followed.
211 Pseudo-element CSS, CodingScripting, Glossary
Editorial review completed.
212 Python CodingScripting, Glossary, Language, Python, glossary, language, programming
Python is a high level general-purpose programming language. It uses a multi-paradigm approach, meaning it supports procedural, object-oriented and some functional programming constructs.
213 RDF CodingScripting, Glossary, Infrastructure, OpenPractices, WebMechanics, glossary
RDF (Resource Description Framework) is a language developed by W3C for representing information on the World Wide Web, such as Webpages. RDF provides a standard way of encoding resource information so that it can be exchanged in a fully automated way between applications.
214 REST Glossary, Rest, WebMechanics
Representational State Transfer (REST) refers to a group of software architecture design constraints that bring about efficient, reliable, and scalable systems.
215 RIL B2G, Firefox OS, Glossary, Infrastructure, Intro, Mobile, Telephony, glossary
RIL (Radio Interface Layer) is a mobile operating system component which communicates between the device's software and the device's phone, radio, or modem hardware.
216 RSS Glossary, OpenPractices, RSS, Sharing, WebMechanics, glossary
RSS (Really Simple Syndication) refers to several XML document formats designed for publishing site updates. When you subscribe to a website's RSS feed, the website sends information and updates to your RSS reader in an RSS document called a feed, so you don't need to check all your favorite websites manually.
217 RTF Composing, Format, Glossary, RTF, Rich Text Format, glossary
RTF (Rich Text Format) is a plain-text-based file format with support for formatting instructions (like bold or italic).
218 Random Number Generator CodingScripting, Glossary, glossary
A PRNG (pseudorandom number generator) is an algorithm that outputs numbers in a complex, seemingly unpredictable pattern. Truly random numbers (say, from a radioactive source) are utterly unpredictable, whereas all algorithms are predictable, and a PRNG returns the same numbers when passed the same starting parameters or seed.
219 Raptor
Raptor: New Performance Tools for Gaia
220 Recursion CodingScripting, Glossary, glossary
An act of a function calling itself. Recursion is used to solve problems that contain smaller sub-problems. A recursive function can receive two inputs: a base case (ends recursion) or a recursive case (continues recursion).
221 Reference CodingScripting, Glossary, NeedsContent, glossary
No summary!
222 Reflow Glossary, WebMechanics
Reflow happens when a browser must process and draw part or all of a webpage again, such as after an update on an interactive site.
223 Regular expression CodingScripting, Glossary, Regular Expression, glossary, l10n:priority
Regular expressions (or regex) are rules that govern which sequences of characters come up in a search.
224 Rendering engine Glossary, Infrastructure, Rendering engine, Web browser engine, glossary
A rendering engine is software that draws text and images on the screen. The engine draws structured text from a document (often HTML), and formats it properly based on the given style declarations (often given in CSS). Examples of layout engines: Blink, Gecko, Edge, WebKit.
225 Repo Glossary, Infrastructure, Intro, Repo, Repository, glossary
No summary!
226 Responsive design DesignAccessibility, Glossary
Responsive web design is a Web development concept focusing on making sites look and behave optimally on all personal computing devices.
227 Responsive web design DesignAccessibility, Glossary, Responsive web design
Responsive web design is a Web development concept focusing on making sites look and behave optimally on all personal computing devices.
228 Robots.txt Glossary, Infrastructure, glossary
Robots.txt is a file, which is usually placed in the root of any website.It decides whether crawlers are permitted or forbidden to get access to the web site.
229 Ruby CodingScripting, Glossary, Ruby
Ruby is an open-source programming language. In a Web context, Ruby is often used server-side with the Ruby On Rails (ROR) framework to produce websites/apps.
230 SCM CodingScripting, Glossary, SCM, glossary
SCM (Source Control Management) is a system for managing source code. Usually it refers to the use of software to handle versioning of source files. A programmer can modify source code files without being afraid of editing out useful stuff, because a SCM keeps track of how the source code has changed and who made the changes.
231 SDP Advanced, Collaborating, Glossary, Infrastructure, Protocol, WebRTC, glossary
SDP (Session Description Protocol) is the standard describing a peer-to-peer connection. SDP contains the codec, source address, and timing information of audio and video.
232 SEO Glossary, Intro, SEO, Search, WebMechanic, glossary, open
SEO (Search Engine Optimization) is the process of making a website more visible in search results.
233 SGML CodingScripting, Composing, Glossary, SGML, glossary, l10n:priority
The Standard Generalized Markup Language (SGML) is an ISO specification made for defining declarative markup languages.
234 SIMD CodingScripting, Glossary, JavaScript, glossary
SIMD (pronounced "seem-dee") is short for Single Instruction/Multiple Data which is one classification of computer architectures . SIMD allows one same operation to be performed on multiple data points resulting in data level parallelism and thus performance gains, for example for 3D graphics and video processing, physics simulations or cryptography, and other domains.
235 SISD CodingScripting, Glossary, glossary
SISD is short for Single Instruction/SIngle Data which is one classification of computer architectures. In SISD architecture, a single processor executes a single instruction and operates on a single data point in memory.
236 SLD Glossary, Infrastructure, glossary
An SLD (Second Level Domain) is a domain that is hierarchically directly below a TLD.
237 SMTP Beginner, Collaboration, Glossary, Infrastructure, Sharing, beginner, glossary
SMTP (Simple Mail Transfer Protocol) is a protocol used to send a new email.  Like POP3 and NNTP, it is a state machine-driven protocol.
238 SOAP Glossary, Infrastructure, SOAP, WebMechanics, glossary
SOAP (Simple Object Access Protocol) is a protocol for transmitting data in XML format. Firefox removed support for SOAP in 2008.
239 SQL CodingScripting, Database, Glossary, Sql, glossary
SQL (Structured Query Language) is a descriptive computer language designed for updating, retrieving, and calculating data in table-based databases.
240 SQL Injection Glossary, Security, Sql, Sql Injection, Webapp, glossary
SQL injection takes advantage of Web apps that fail to validate user input. Hackers can maliciously pass SQL commands through the Web app for execution by a backend database.
241 STUN Glossary, Infrastructure, STUN, WebMechanics, WebRTC, glossary
STUN (Session Traversal Utilities for NAT) is an auxiliary protocol for transmitting data around a NAT (Network Address Translator). STUN returns the IP addressport, and connectivity status of a networked computer behind a NAT.
242 SVG Beginner, CodingScripting, Glossary, Graphics, SVG, beginner, glossary
Scalable Vector Graphics (SVG) is a 2D vector image format based on an XML syntax.
243 SVN Collaborating, Glossary
Apache Subversion (SVN) is a free source control management (SCM) system. It allows developers to keep a history of text and code modifications. Although SVN can also handle binary files, we do not recommend that you use it for such files.
244 Scope CodingScripting, Glossary, glossary
The current context of execution. The context in which values and expressions are "visible," or can be referenced. If a variable or other expression is not "in the current scope," then it is unavailable for use. Scopes can also be layered in a hierarchy, so that child scopes have access to parent scopes, but not vice versa.
245 Second-level Domain Glossary, Infrastructure
An SLD (Second Level Domain) is a domain that is hierarchically directly below a TLD.
246 Server Glossary, Infrastructure, Networking, Protocol, Server, glossary
A hardware server is a shared computer on a network that provides services to clients.  A software server is a program that provides services to client programs.
247 Session Hijacking Glossary, Security, glossary, session hijacking
Session hijacking occurs when an attacker takes over a valid session between two computers. The attacker steals a valid session ID in order to break into the system and snoop data.
248 Shim CodingScripting, Glossary
shim is a piece of code used to correct the behavior of code that already exists, usually by adding new API that works around the problem. This differs from a polyfill, which implements a new API that is not supported by the stock browser as shipped.
249 Signature Disambiguation, Glossary
The term signature can have several meanings depending on the context. It may refer to:
250 Signature (functions) CodingScripting, Glossary, Java, JavaScript, glossary
A function signature (or type signature, or method signature) defines input and output of functions or methods.
251 Signature (security) Cryptography, Glossary, Privacy, Security
A signature, or digital signature, is a protocol showing that a message is authentic.
252 Simple header Glossary, HTTP, Infrastructure, glossary
A simple header is an HTTP header. Its name is either Accept, Accept-LanguageContent-Language, or `Content-Type`. The MIME type of its parsed value (ignoring parameters) is either application/x-www-form-urlencoded, multipart/form-data, or text/plain.
253 Smoke Test Composing, Glossary, Intro, QA, Testing, glossary
A smoke test consists of functional or unit tests of critical software functionality. Smoke testing comes before further, in-depth testing.
254 Specification Glossary, OpenPractices, Standardization, glossary
specification is a document that lays out in detail what functionality or attributes a product must include before delivery.
255 Stacking context CSS, CodingScripting, DesignAccessibility, Glossary
Stacking context refers to how elements on a webpage appear to sit on top of other elements, just as you can arrange index cards on your desk to lie side-by-side or overlap each other.
256 State machine CodingScripting, Finite, Glossary, Input, Mealy, Moore, State Machine, Turing Machine, glossary, input
A state machine is a mathematical abstraction used to design algorithms. A state machine reads a set of inputs and changes to a different state based on those inputs.
257 Statement Beginner, CodingScripting, Glossary, beginner, glossary
In a computer programming language, a statement is a line of code commanding a task. Every program consists of a sequence of statements.
258 Static typing CodingScripting, Glossary, glossary
A statically-typed language is a language (such as Java, C, or C++) where variable types are known at compile time and must be expressly indicated by the programmer.
259 String Beginner, CodingScripting, Glossary, String, beginner, glossary
In any computer programming language, a string is a sequence of characters used to represent text.
260 Symbol Glossary, JavaScript, Sharing
A Symbol is a primitive data type whose instances are unique and immutable. In some programming languages they are also called atoms.
261 Synchronous Glossary, Web, WebMechanics
Synchronous refers to real-time communication, that is, where each party receives (and if necessary, processes and replies to) messages nearly as soon as they are sent out.
262 Syntax CodingScripting, Glossary
Syntax specifies the required combination and sequence of characters making up correctly structured code. Syntax varies from language to language (e.g., syntax is different in HTML and JavaScript). Syntax applies both to programming languages (commands to the computer) and markup languages (document structure information).
263 Syntax error CodingScripting, Glossary
An exception caused by the incorrect use of a pre-defined syntax.  Syntax errors are detected while compiling or parsing source code.  For example, if you leave off a closing brace (}) when defining a JavaScript function, you trigger a syntax error.  Browser development tools display JavaScript and CSS syntax errors in the console.
264 TCP Glossary, Infrastructure, Networking, TCP, Transmission Control Protocol, data
TCP (Transmission Control Protocol) is an important network protocol that lets two hosts connect and exchange data streams.  TCP guarantees the delivery of data and packets in the same order as they were sent.  Vint Cerf and Bob Kahn, who were DARPA scientists at the time, designed TCP in the 1970s.
265 TLD Glossary, Web, WebMechanics
A TLD (top-level domain) is the most generic domain in the Internet's hierarchical DNS (domain name system). A TLD is the final component of a domain name, for example, "org" in
266 TLS Cryptography, Glossary, Infrastructure, Security
Transport Layer Security (TLS), previously known as Secure Sockets Layer (SSL), is a protocol used by applications to communicate securely across a network, preventing tampering with and eavesdropping on email, web browsing, messaging, and other protocols.
267 TURN Glossary, Infrastructure, TURN, WebMechanics, WebRTC, glossary
TURN (Traversal Using Relays around NAT) is a protocol enabling a computer to receive and send data from behind a Network Address Translator (NAT) or firewall.
268 Tag CodingScripting, Glossary, HTML, Intro
In HTML a tag is used for creating an element.  The name of an HTML element is the name used in angle brackets such as <p> for paragraph.  Note that the end tag's name is preceded by a slash character, "</p>", and that in empty elements the end tag is neither required nor allowed. If attributes are not mentioned, default values are used in each case.
269 Telnet
Editorial review completed.
270 Three js Browser, CodingScripting, JavaScript, Programming Language, three.js
three.js is a JavaScript-based WebGL engine that can run GPU-powered games and other graphics-powered apps straight from the browser. The three.js library provides many features and APIs for drawing 3D scenes in your browser.
271 Trident Browser, Glossary, Infrastructure, Trident
Trident (or MSHTML) is a layout engine that powers Internet Explorer.  A Trident fork called EdgeHTML has replaced Trident in Spartan and Internet Explorer 11.
272 Truthy CodingScripting, Glossary, JavaScript
In JavaScript, a truthy value is a value that translates to true when evaluated in a Boolean context. All values are truthy unless they are defined as falsy (i.e., except for false, 0, "", null, undefined, and NaN).
273 Type CodingScripting, Glossary, JavaScript
Type is a characteristic of a value affecting which operations on that value are valid. For example, an integer can be multiplied by an integer, but not by a string.
274 Type Conversion CodingScripting, Glossary, Type casting, Type conversion
Type conversion (or typecasting) means transfer of data from one data type to another. Implicit conversion happens when the compiler automatically assigns data types, but the source code can also explicitly require a conversion to take place.  Simple examples: given the instruction 5+2.0, the integer 5 is implicitly typecasted into floating point, but given the instruction Number("0x11"), the string "0x11" is explicitly typecasted as the number 17.
275 UDP Glossary, Infrastructure, UDP
UDP (User Datagram Protocol) is a longstanding protocol used together with IP for sending data when transmission speed and efficiency matter more than security and reliability.
276 URI Glossary, HTTP, Landing, Search, URI, URL
A URI (Uniform Resource Identifier) is a string that refers to a resource. The most common are URLs, which identify the resource by giving its location on the Web. URNs, by contrast, refer to a resource by a name, in a given namespace, e.g. the ISBN of a book.
277 URL Glossary, Infrastructure
Uniform Resource Locator (URL) is a text string specifying where a resource can be found on the Internet.
278 URN Glossary, Intro, Navigation, urn
URN (Uniform Resource Name) is a URI in a standard format, referring to a resource without specifying its location or whether it exists. This example comes from RFC3986: urn:oasis:names:specification:docbook:dtd:xml:4.1.2
279 UTF-8 CodingScripting, Glossary, HTML, JavaScript, Utf-8
UTF-8 (UCS Transformation Format 8) is the World Wide Web's most common character encoding.  Each character is represented by one to four bytes. UTF-8 is backward-compatible with ASCII and can represent any standard Unicode character.
280 Usenet Glossary, WebMechanics, glossary
Usenet is an internet discussion system where each post is duplicated on many servers. The equivalent of Internet forums in its day, Usenet functioned like a bulletin board system.
281 User agent Glossary, User-agent, WebMechanics, user agent
A user agent is a computer program representing a person, for example, a browser in a Web context.
282 Validator Beginner, Glossary, Security
A validator is a program that checks for syntax errors in code. Validators can be created for any format or language, but in our context we speak of tools that check HTMLCSS, and XML.
283 Value CodingScripting, Glossary, NeedsContent
In the context of data or an object wrapper around that data, the value is the primitive value that the object wrapper contains. In the context of a variable or property, the value can be either a primitive or an object reference.
284 Variable CodingScripting, JavaScript
A variable is a named location for storing a value. That way an unpredictable value can be accessed through a predetermined name.
285 Vendor Prefix CodingScripting, Glossary
Browser vendors sometimes add prefixes to experimental or nonstandard CSS properties, so developers can experiment but changes in browser behavior don't break the code during the standards process. Developers should wait to include the unprefixed property until browser behavior is standardized.
286 Viewport CodingScripting, Glossary
A viewport represents a polygonal (normally rectangular) area in computer graphics currently being viewed.
287 VoIP Glossary, Infrastructure, VoIP, glossary
VoIP (Voice over Internet Protocol) is a technology used to transmit voice messages over IP (Internet Protocol) networks. Common VoIP packages include Skype, Msn Messenger, Yahoo and many more. Everything transferrred through VoIP is digital. It is also known as IP telephony, or broadband telephony. The main reason for using VoIP technology is because of cost.
288 W3C Community, Consortium, Glossary, Intro, W3C, Web consortium
The World Wide Web Consortium (W3C) is an international body that maintains Web-related rules and frameworks.
289 WAI DesignAccessibility, Glossary
WAI or Web Accessibility Initiative is an effort by the World Wide Web Consortium (W3C) to improve accessibility for people with various challenges, who may need a nonstandard browser or devices.
290 WCAG Accessibility, DesignAccessibility, Glossary, WCAG, Web Guidelines
Web Content Accessibility Guidelines (WCAG) are a recommandation published by the Web Accessibility Initiative group at the W3C. They outline a set of guidelines for making content accessible primarily for people with disabilities but also for limited-resource devices such as mobile phones.
291 WHATWG Community, Glossary, HTML, HTML5, WHATWG, Web
The WHATWG (Web Hypertext Application Technology Working Group) is an organization that maintains and develops HTML and APIs for Web applications. Former employees of Apple, Mozilla, and Opera established WHATWG in 2004.
292 WWW Glossary, Infrastructure, WWW, WorldWideWeb, glossary
The World Wide Web—commonly referred to as WWW, W3, or the Web—is a system of interconnected public webpages accessible through the Internet. The Web is not the same as the Internet: the Web is one of many applications built on top of the Internet.
293 Web standards Glossary, Infrastructure, Web Standards, standards, web specifications
Web standards are rules established by international standards bodies and defining how how the Web works (and sometimes controlling the Internet as well).
294 WebDAV Glossary, Infrastructure
WebDAV (Web Distributed Authoring and Versioning) is an HTTP Extension that lets web developers update their content remotely from a client.
295 WebGL Advanced, CodingScripting, Glossary, Web Graphics, WebGL
WebGL (Web Graphics Library) is a JavaScript API that draws interactive 2D and 3D graphics.
296 WebIDL CodingScripting, Glossary, WebIDL
WebIDL is a language for building interfaces in Web applications.
297 WebKit Browser, Glossary, Intro, Web, WebKit, WebMechanics
WebKit is a framework that displays properly-formatted webpages based on their markup. Apple Safari depends on WebKit, and so do many mobile browsers (since WebKit is highly portable and customizable).
298 WebM Glossary, WebM, glossary
WebM is royatly free and is an open web video format natively supported in Mozilla Firefox.
299 WebP Beginner, Glossary, WebP, beginner, glossary
WebP is a lossless and lossy compression image format developed by Google.
300 WebRTC CodingScripting, Glossary, Infrastructure, P2P, VoIP, Web, WebRTC
WebRTC (Web Real-Time Communication) is an API invoked by video-chat, voice-calling, and P2P-file-sharing Web apps.
301 WebSockets Connection, Glossary, Infrastructure, Networking, Protocols, Web, WebSocket, glossary
WebSocket is a protocol that allows for a persistent TCP connection between server and client so they can exchange data at any time.
302 World Wide Web Glossary, Infrastructure, WWW, World Wide Web
The World Wide Web—commonly referred to as WWW, W3, or the Web—is a system of interconnected public webpages accessible through the Internet. The Web is not the same as the Internet: the Web is one of many applications built on top of the Internet.
303 Wrapper CodingScripting, Glossary, NeedsContent
An object that contains a primitive, whose sole purpose is to provide methods and properties to operate on that primitive. The wrapper's toString method returns the primitive.
304 XForm CodingScripting, Glossary, Obsolete, XForms
XForms is a convention for building Web forms and processing form data in XML format. No major browser supports XForms any longer—we suggest using HTML5 forms instead.
305 XHTML CodingScripting, Glossary, XHTML
HTML can travel over the network to a browser either in HTML syntax or an XML syntax called XHTML.
306 XInclude
XML Inclusions (XInclude) is a W3C Recommendation to allow inclusion of XML more different sources in a more convenient fashion than XML external entities. When used in conjunction with XPointer (Firefox supports a subset of it, and is used in the code sample below), XInclude can also target just specific portions of a document for inclusion. Firefox does not support it natively, but the following function aims to allow its use with documents passed into it.
307 XLink
XLink is a W3C standard which is used to describe links between XML and XML or other documents. A number of its behaviors are left to the implementation to determine how to handle.
308 XML CodingScripting, Glossary, XML
eXtensible Markup Language (XML) is a generic markup language specified by the W3C. The IT industry uses many languages based on XML as data-description languages.
309 XPath CodingScripting, Glossary, XML, XPath
XPath is a language used for accessing sections and content in an XML document.
310 XQuery CodingScripting, Glossary, XML, XQuery
XQuery is a computer language for updating, retrieving, and calculating data in XML databases.
311 XSLT CodingScripting, Glossary, XML, XSLT
eXtensible Stylesheet Language Transformations (XSLT) is a declarative language used to convert XML documents into other XML documents, HTML, PDF, plain text, and so on.
312 ltr Composing, Glossary, Localization
Technical review completed.
313 mime Beginner, Glossary, MIME, beginner, glossary
MIME Multipurpose internet mail extensions supports text in other forms beside ASCII and non-text attachments such as audio, video and images.
314 non-normative Glossary, Specification, Standardization, glossary
Software specifications often contain information marked as as non-normative or informative, which means that those are provided there for the purpose of helping the reader understand the specification better or to show an example or a best pracice, and not needed to be followed as a rule. Sections that contain official part of the specification that must be followed are often marked as normative.
315 rtl Composing, Glossary, Localization
Technical review completed.
316 undefined CodingScripting, Glossary, NeedsContent
A primitive value automatically assigned to variables that have just been declared or to formal arguments for which there are no actual arguments.

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