If the sun has color bands, then I'd think it was a problem with the color depth of the viewed image. 8 or 16 bit color, for instance, won't render nice gradations, but rather solid bands of color. This is typical of non-dithered gif images, but not usually of jpgs.

If the sun has blocks of color, then it might be compression. Highly compressed jpg images will start to display blocks, or squares of color. AOL uses a process on it's servers to re-compress an image in order to lower the filesize, but it plays havoc with the quality of the delivered picture. This happens not only on images served by AOL, but also images called from other servers for AOL clients. I've never heard of Geocities doing the same thing, though.

I'm assuming that other images viewed in a browser on your computer look ok, but this one is problematic. Is that right? If so, I'm not sure why this particular image is being rendered so poorly on your machine. It looks ok on mine.

What browser do you usually use? Some recent versions of IE have a built-in image re-scaling function which could sometimes cause an image to appear distorted. I wouldn't have thought it would cause banding, though.