The W3C Cascading Style Sheets working group has posted the candidate recommendation of Media Queries:
HTML4 and CSS2 currently support media-dependent style sheets tailored for different media types. For example, a document may use sans-serif fonts when displayed on a screen and serif fonts when printed. "Screen" and "print" are two media types that have been defined. Media Queries extend the functionality of media types by allowing more precise labeling of style sheets.
A Media Query consists of a media type and one or more expressions to limit the scope of style sheets. Among the media features that can be used in media queries are "width", "height", and "color". By using Media Queries, presentations can be tailored to a specific range of output devices without changing the content itself.
