But however URL channels wont give you a perfect idea for that you will have to create channels for each ads. This will also help you to know which format is doing better for you.
From those of your signature, only the "Itchy Butt" site contains adsense. It must have come from that site.
Ad channels will help refine the location if he's using more than one ad block on a page...for me URL channel is enough since I don't put more than one per page but probably for the bulk of people a combination of the two would really narrow it down.
I just broke $3.00 for 1 click on one of my websites... I just need to get more traffic so I can get more of these 3 dollar clix