CSS

Cascading Style Sheets (CSS) are a stylesheet language used to describe the presentation of a document written in HTML or XML (including XML dialects like SVG or XHTML). CSS describes how elements should 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 is a recommendation, and CSS3, now split into smaller modules, is progressing on the standardization 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.

ocumentation and tutorials

CSS key concepts

Describes the syntax and forms of the language and introduces fundamentals like specificityand 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 everything from the basics of styling HTML to assorted 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 CSS is valid. The service at OnlineWebCheck.com also does the same. These are invaluable debugging tools.
• Firefox Developer Tools allow viewing and editing live CSS of a page via the Inspector and Style Editor tools.
• Firebug extension for Firefox, 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.
• Web Developer extension for Firefox also allows to watch and edit live CSS on watched sites. Simpler than Firebug, though less powerful.
• Miscellaneous CSS tools.