Well, I'll be - where did that double-colon come from? It didn't come over the sea and it wasn't in search of India. No, it came with CSS3 and it is not, as some people believe, the new single-colon.
The double-colon is W3C's attempt to clarify the distinction between pseudo-elements and pseudo-classes, both of which received the same single-colon treatment in CSS1 and 2. Basically...
::after
::before
::first-letter
::first-line
::selection
... not all of which are accessible on deviantART - are pseudo-elements. The pseudo-classes (:active, :hover, etc.) are still subject to the single-colon.
Now I have good news and bad news. The bad new