What are the relevant CSS standards?

There are three CSS recommendations from the W3C: CSS1, CSS2, and CSS3. Most modern browsers support a large part of CSS1 and CSS2, as well as parts of CSS3. You can find out more at http://www.w3.org/Style/CSS/. If you’re curious about how well your browser supports CSS or the effect that properties have in real browsers, you can check out the CSS test suites at http://www.w3.org/Style/CSS/Test/. CSS2 and CSS3 include a number of additional selectors.