You could probably design something a little like that in Publisher using
the drawing tools or border styles but it wouldn't technically be like this
site example. Source code for a page and image info is right in front of you
to learn from.
Just right click the image on the page to learn about it. For example when I
right clicked on this site I then saved background image to my pc. Then look
at the image. When you look at this image you see it's a thin (maybe 1 pixel
wide) graphic with a top color and then the bottom color. If you want to
create graphics like this you need a graphics program or a graphic designer
to assist you.
The thing to know about a background image is that the browser tiles a
background image left to right top to bottom. Hence why this image is a
"slice" and has such a height. This "slice" gets tiled across the page. If
you create your own slice image just set it as your Publisher web background
image.
David Bartosik - [MSFT MVP]
www.publishermvps.com
www.davidbartosik.com