From: Daniel Piechnick
Ok I can't see what you're talking about, but I think I know what it is. It's probably a gradient, set as a background. In Photoshop, just make an image one pixel tall, and as wide as your main table. Choose grey and black as your foreground and background colours, and apply the Gradient Tool across your image. Then save it for the web, and then set it as the background of your main table. You can also do this to make kinda funky desktop backgrounds.