need help building a html table with a div that floats as the page scrolls

The best way for me to explain what exactly I am trying to accomplish is by taking a look at this page.. you will see the functionality in the amazing table there..

Please show me the way WPMU GODS!!! I have tried since last night and all day.. I can get some if working as you see here

but that table has some magic sauce happening.. youll see on roll over it looks like there is a a seperate div holding the image and description and some how whats inside the div magically changes as you scroll the table and the div some how floats as you go.. or so it seems..

any advice on this would be welcomed.