Actually image size varies a great deal in depth of color Chris. Some images weigh less as jpg, some weigh less as gif, some weigh less as png. I typically check all 3 when saving for web applications and it varies considerably dependent upon how many colors you have in the image. Easiest way to check it is of course in Photoshop, using Save for Web, with 4 up comparison. In example, my avatar weighs in at 3.27 K as a jpg file at 50% quality. If I save it as gif or png-8, at 168 colors, (again 50% quality in gif and png-8), it weighs in at 5.85 and 5.25 K respectively. And, I lose more resolution in the image.