What's this image tag for?

Hey all, I'm building a site for a client that is using this system called Linkshare to link to web sites for stores and it's one of those deals where they provide the link code so my client gets credit for sending the person to the store's site. Common enough, but there is one thing about their code I'm a bit confused about. Here is one of their links you put in your code to link to a store: <a href="http://click.linksynergy.com/fs-bin/click?id=5sJlsTOpnzE&offerid=115126.10000505&type=4&subid=0"><IMG alt="Sharper Image" border="0" src="http://www.sharperimagespecials.com/banners/Promos/11_Nov06/fshproplus_1106_125x125.gif"></a><IMG border="0" width="1" height="1" src="http://ad.linksynergy.com/fs-bin/show?id=5sJlsTOpnzE&bids=115126.10000505&type=4&subid=0"> You'll notice they provide an image for you to display embedded in the <a href="..."> </a> tags, simple enough, but I can't figure out what that second IMG tag is for with the little 1 x 1 image. Since it's outside the actual link, I don't really see what it accomplishes. Anyone with experience with these things, or just any idea why it's there would sure help clear the fog from my brain on this one. Much thanks! -- Skip Evans Big Sky Penguin, LLC 61 W Broadway Butte, Montana 59701 406-782-2240