In http://lists.w3.org/Archives/Public/www-style/2009Aug/0128.html the CSS working group resolved that @media rules should not allow empty media lists. I wrote a patch for it immediately, but never got around to filing a bug.
(The minutes aren't all that clear, but the discussion was clear that the change was specific to @media and not a general media queries change.)
(I'll attach the patch once it passes try server; it requires at least one unit test adjustment and maybe more.)
Created attachment 441318 [details] [diff] [review]
Passes all unit tests on try on Linux and Mac. Still waiting for Windows results, but no reason to think they'll be different.
Comment on attachment 441318 [details] [diff] [review]
The CSS working group decided at yesterday's telecon that it should be valid after all. So this is now invalid.