The first implementation of CSS was initially drawn up in 1996
and then released in 1999. By 2001 all new browser releases
supported it, but even so the standard was once again revised
in 2008. At the same time (beginning in 1998) CSS 2 was already
being drawn up, and the standard was eventually completed in
2007 - but revised again in 2009. Then there's CSS 3, which
commenced development in 2001, and of which some features were
proposed only as recently as 2012. Therefore the development
process will likely continue for some time before a final
recommendation for CSS 3 is agreed. And even though CSS 3 isn't
yet complete, people are already beginning to put forward
suggestions for CSS 4 (and even ideas for HTML6 too).