You need to use the onScroll handler of the body tag. Then using some creative math you can position an object on the page. Usually, you need some master container object for everything you want to have move (div and tables work well).
Take a look here for an example of just what you are looking for...
http://www.geekdork.com/samples/dhtm...ioningTest.htm
Peter
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Work smarter, not harder.