How many Pseudo-classes are there in CSS?

Question

How many Pseudo-classes are there in CSS? What are they?

Answer 1

See 5.10 Pseudo-elements and pseudo-classes of the CSS2 spec.

CSS3 selectors are in Last Call status. See 6.6 Pseudo-classes, and 7 Pseudo elements.

Answer 2

A bunch of useful ones.

I mostly use: :hover :active but :before :after and :first-child are useful too.