3D- I'm not aware of transparency fot JPGs, but the usally rule of thumb is use JPG for all color images unless you need the special features of GIF, like animation and transparency, and save as medium or less quality (but I can't bring myself to use low, I don't do low quality images!) Make sure you set the background color for the page, don't let the browser use its default- you should even set a background color if you use wallpaper, so your text is readable while the wallpaper loads. Also remember, a GIF is only 256 colors (max), so if you use one of the "system" or "websafe" palettes it might not have the right colors in it.