How to have an opaque background image on a div?

[BoTGoD]

I have a \[code\]<div>\[/code\] which contains a bunch of \[code\]<p>\[/code\]s and would like to have an opaque background image behind text, scaled to fill the entire \[code\]<div>\[/code\].How do I do that, please? (and do I have to worry about browsers which do not support CSS3?)