transparency in tables

[eddievedderfan]

I was just wondering if anyone could help me figure out how to achieve the table transparency on this site [cincinnati-oh.gov]. The image also rotates between 5 or so images and works in IE, Safari, & Netscape. I would like to be able to do something like this on a site I am working on, but can't figure it out.

[krieves]

I wonder if, instead of using transparent tables, the background image in each of the cells is changing to match the main image. It's a nice effect.

I'm guessing that "choose_css.js" is used to rotate a different stylesheet that defines the images. That would make sense.