by Albert Wiersch » Fri May 30, 2008 1:59 pm
Hello,
It seems like the 'background-position' part of the 'background' property is at question. In your CSS this is "center left".
CSS 2.1 says 'background-position' can be:
[ [ <percentage> | <length> | left | center | right ] [ <percentage> | <length> | top | center | bottom ]? ] | [ [ left | center | right ] || [ top | center | bottom ] ] | inherit
With the relevant part:
[ left | center | right ] || [ top | center | bottom ]
Your CSS should be correct because "||" means one or more of the separated options must occur, in any order.
So it looks like this is a bug in CSE HTML Validator. I've fixed this in v8.9913.

Albert Wiersch