It's a horizontal gradient JPEG background with the blue color encompassing a majority of the JPEG, then they surrounded it with a black bg behind it, for larger monitors so it looks like the black is going on farther on bigger monitors.
My coder knows how to do it, since we tested it once to try and find a solution to our issue. I do not know how though, as I didn't do it. BUT, I know a solution that isn't fun.
You can make the image in photoshop like this:
http://img.photobucket.com/albums/v3..._666/examp.jpg
Then copy the styles, and change the bg image here to the screen resolutions of the diff users you have, and have each style be titled with Dark Red (1280 x 1060) or whatever, so people can choose the style based on there screen res. This unfortunately is the only solution for us. But the easier way would be to use a border afterwards of black and then it will fill in whatever extra space based upon users monitors to black, making it look good.