http://www.w3.org/TR/1999/REC-CSS1-19990111.html#comments
> Comments cannot be nested. For a CSS1 parser, a comment is equivalent to whitespace.
http://www.w3.org/TR/1998/REC-CSS2-19980512/syndata.html#comments
> Comments begin with the characters "/*" and end with the characters "*/". They may occur anywhere between tokens, and their contents have no influence on the rendering. Comments may not be nested.