CSS

Cascading Style Sheets (CSS) is a style sheet language that allows authors and users to attach style (e.g., fonts, spacing, and aural cues) to structured documents.  By separating the presentation style of documents from the content of documents, CSS simplifies Web authoring and site maintenance. 

CSS supports media-specific style sheets so that authors may tailor the presentation of their documents to visual browsers, aural devices, printers, braille devices, handheld devices, etc. This specification also supports content positioning, downloadable fonts, table layout, features for internationalization, automatic counters and numbering, and some properties related to user interface.

A CSS rule consists of two main parts; a selector that specifies to which element formatting will be applied and a declaration of the style to be applied. The declaration has two parts: property  and value.  CSS was originally designed to support the formatting of HTML documents.  Today CSS enables formatting of structured documents that are either HTML or XML applications).

Sample CSS Rule:

h1 {font-color: blue}

In this rule, "h1" is the selector, "font-color" is the property and "blue" is the value.

CSS 2.0 is a W3C Recommendation.  CSS 3.0 is currently a Working Draft.