CSS versions

W3C CSS1 : 1996

CSS2 finalized in May 1998

CSS2 includes all CSS1 properties and adds around 70 of its own

CSS2 supports media-specific style

visual browsers, aural devices, printers, braille devices, handheld devices

CSS 2.1 : 25/2/04

corrects errors in CSS2 and adds a few highly requested features originally planned for CSS3, which have already been widely implemented.

But most of all CSS 2.1 represents a "snapshot" of CSS usage: it consists of all CSS features that are implemented interoperably for HTML and XML at the date of publication of the Recommendation.

CSS 3 in progress

This specification defines Cascading Style Sheets, level 2.1 (CSS2). CSS2 is a style sheet language that allows authors and users to attach style (e.g., fonts, spacing, and aural cues) to structured documents (e.g., HTML documents and XML applications). By separating the presentation style of documents from the content of documents, CSS2 simplifies Web authoring and site maintenance.
CSS2 builds on CSS1 and, with very few exceptions, all valid CSS1 style sheets are valid CSS2 style sheets. CSS2 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.

Source : http://www.cs.tcd.ie/Benjamin.Jung/Download/QuickReference/CSS-2/

 

Cascading Style Sheets is formally described in two specifications from W3C: CSS1 and CSS2. CSS1 was issued in December 1996 and describes a simple formatting model mostly for screen-based presentations. CSS1 has around 50 properties (for example color and font-size). CSS2 was finalized in May 1998 and builds on CSS1. CSS2 includes all CSS1 properties and adds around 70 of its own, such as properties to describe aural presentations and page breaks. The CSS specifications :
W3C CSS1 : http://www.w3.org/TR/REC-CSS1
W3C CSS2 : http://www.w3.org/TR/REC-CSS2
Source : http://www.w3.org/Style/LieBos2e/enter/