CSS level 2 (CSS2) The CSS2 spec came out in 1998 and is the most widely adopted by browser makers. Level 2 includes all the attributes of the previous two versions, plus an increased emphasis on international accessibility and the capability to specify media specific CSS. In 2006, the W3C published an updated version: CSS Level 2.1, which corrected some errors, clarified a few issues, and included specifications for features that had already been implemented in some browsers. CSS2.1 has effectively replaced CSS2. CSS level 3 (CSS3) Unlike CSS1 and 2, a single, comprehensive CSS3 does not exist. Instead, rather than trying to release the entire specification at once, the CSS Working Group has split the spec into a series of modules; each of which has its own developmental timeline.