create channels and assign the ads accordingly. You will be able track exactly which ad is is getting clicked and how much $ its getting u.
Give each of them a channel name, track them by channels. Put different adsense ads in your site with different channel names. Example. make one ad link with channel name "links ad top nav" make another ad link with channel name "links ad side nav" make one ad unit with channel name "unit ad for content" make another ad unit with channel name "unit ad side nav" You will then be able to track every ads individual impression, clicks, ctr, earnings etc..
that's true - it's not possible to find out which Ad is click but by organizing your channels you get more info like CTR. Just google "channels" for more info