- Incorporating errata found in 2.0;
- Removing version 2.0 features which have been rejected by the CSS community;
- Removing version 2.0 features which will be obsolete in version 3.0;
- Adding a few new property values;
- Modifying the specification to reflect common practice.
Thus, while it is not the case that a CSS2 style sheet is necessarily forwards-compatible with CSS 2.1, it is the case that a style sheet restricting itself to CSS 2.1 features is more likely to find a compliant user agent today and to preserve forwards compatibility in the future. While breaking forward compatibility is not desirable, we believe the advantages to the revisions in CSS 2.1 are worthwhile.FYI: This is still a working draft, not yet a W3C recommendation. [from W3C News]