I know this is a really old thread, but it shows up at the top in Google, so here's another option.
This one is pure CSS, and doesn't require any extra HTML.
box-shadow: inset 0 0 0 1000px rgba(0,0,0,.2);
There are a surprising number of uses for the box-shadow feature.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…