Just read this article.... But it's really not. Mozilla and Firefox already support some of the selectors that will be available in CSS level 3 and Internet Explorer 7 is expected to be close behind in this support as well. While it might be too soon to start relying on these selectors, becoming familiar with them won't hurt, and it could help a lot. For details follow this URL: http://webdesign.about.com/od/css3/a/aa062603.htm
There are some technical errors in that article. My opinion: Skip the About.com article and just go straight to the source. W3C Working Draft -- Selectors