This should be pretty simple, but I'm not an expert with DHTML/CSS.
Basically, I have thumbnail images of artworks that are shown on a page and I want the title and artist name to overlay the image when a user rolls over it.
Ideally I'd like a blue opaque background overlay on top of the image with white text on top of the blue background. eg the blue background is opaque and sits on top of the image. You can still see the image, which is important for usability so that the user doesn't lose context as soon as they rollover. It also acts to make the white text clearer in case the artwork image has a lot of white in it.