Sorry to jump into a thread here, but I have tried all kinds of combinations of locations and none seem to take effect.
I've put the above code into base.css, style.css, and in the custom code box (not all at the same time of course). None of these produces a white background. If I turn off the custom background color under Global Options, then it goes from a brown I had selected back to medium gray.
Seems like there is a master stylesheet trumping everything we do here but I can't see anything in Firebug. (I figured it could be a silly plugin stylesheet but don't see one.)
(PS: I'm well-versed in CSS, PHP, etc., so it's not a code error on this side -- I don't think!