Accessibility Features of CSS
http://www.w3.org/TR/CSS-access

W3C

Abstract:

This document summarizes the features of the Cascading Style Sheets (CSS), level 2 Recommendation ([CSS2]) known to directly affect the accessibility of Web documents. Some of the accessibility features described in this document were available in CSS1 ([CSS1]) as well. This document has been written so that other documents may refer in a consistent manner to the accessibility features of CSS.