CSS

Cascading Style Sheets, most of the time abbreviated as CSS, is a stylesheet language used to describe the presentation of a document written in HTML or XML (including various XML languages like SVG or XHTML. CSS describes how the structured element must be rendered on screen, on paper, in speech, or on other media.

CSS is one of the core languages of the open web and has a standardized W3C specification. Developed in levels, CSS1 is now obsolete, CSS2.1 a recommendation and CSS3, now split into smaller modules, is progressing on the standard track.

  • CSS Reference

    An exhaustive reference for seasoned Web developers describing every property and concept of CSS.

  • CSS Tutorial

    A step-by-step introduction to help complete beginners get started. It presents all the needed fundamentals.

  • CSS3 Demos

    A collection of demos showing the latest CSS technologies in action: a boost for the creativity.

Documentation and tutorials

CSS key concepts
Describes the syntax and forms of the language and introduces fundamentals like specificity and inheritance, the box model and margin collapsing, stacking and block-formatting contexts, or the initial, computed, used and actual values. Entities like CSS shorthand properties are also defined.
CSS developer guide
Articles to help you learn CSS techniques to make your content shine.
Common CSS questions
Answers to common questions about CSS.

Tools for CSS development

  • The W3C CSS Validation Service checks if a given CSS is valid. It is an invaluable debugging tool.
  • Firefox' Firebug extension, a popular extension of that navigator that allows to edit live CSS on watched sites. Very practical to test some changes, though this extension does much more.
  • Firefox' Web Developer extension also allows to watch and edit live CSS on watched sites. Simpler than Firebug, though less powerful.
  • Firefox' EditCSS extension allows editing CSS in the sidebar.
  • CSS Text-decoration Level 3 reached the Candidate Recommandation status, defining that the text-decoration-* and text-emphasis-* properties. The long known text-shadow is also defined in it. (August 1st, 2013)
  • Gecko's now support background-origin: local. It will be available from Firefox 25 (and already is in Nightly). (July 25th, 2013)
  • Pointer Events reached the Candidate Recommandation status, meaning that the CSS property touch-action, currently only implemented in IE10 (with the -ms- prefix), is no more experimental. (May 6th, 2013)
  • Gecko's support of flexible boxes has been adapted to match a recent specification clarification: from Firefox 23 ::before and ::after will be flex items, and as such can be repositioned using order and align-self. (May 3rd, 2013)

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