Easy as pie, Uncle Moe.
Set the background color of your webpage for the same color as the bottom of your gradient. When designing your interface, leave enough room on one side of the document so that you can take a 5-pixel or so wide piece of it from top to bottom, and save it as a gif or a jpg. It is already the same height as your graphics, as you have laid out your page design. It's not wide enough to cover a whole page, but it is if you tile it! ;)
Just remember to tile it horizontally, but not vertically. And don't use diagonal gradients.
P.S. - If you don't understand what I mean, do a search on
www.webmonkey.com
"A criminal is a person with predatory instincts who has not sufficient capital to form a corporation." --Howard Scott