Hey sharp4runr, the way revenue is generated varies between the ads. Tire Rack pays a 6% commission if you click on their banner and then buy something. Partznet pays a fixed monthly advertising fee, no additional revenue is generated by purchases, same with second skin audio. The ads that say "ads by Google" next to them pay by the click through so yes for those it helps everytime you just click on them. I've got a little arrangement with a buddy of mine though - he gets all the revenue from the Google ads in exchange for giving me free server space for this site
Oh and the capital one ad pays only if you get a loan through them and so far it hasn't generated a dime
Thanks for asking