Right now I'd be far more inclined to still use SitePoint's, as their reference appears to be much more through, including extensive commentary on cross-browser

Right now I'd be far more inclined to still use SitePoint's, as their reference appears to be much more through, including extensive commentary on cross-browser differences. See http://reference.sitepoint.com/css/background http://reference.sitepoint.com/css/background http://code.google.com/docreader/#p http://code.google.com/docreader/#p(doctype)s(doctype)t(BackgroundCSSProperty) This isn't to say that Google's documentation project won't get better, as it is an open project; but right now it's borderline useless IMHO.