If you structure your site well, the when the Adsense shows the Ads will be totally relevant and pick up your keywords accurately. This means that people are more likely to click on your ads as they are totally relevant. To structure your site well - keep all pages that have a common theme in their own individual directories. Does anyone else have any tips regarding relevance of Adsense Ads?
Adsense earnings depends on how you have placed the ads on your site because the improper placement could create problems in clicks..
its not only adsense ads placement.. you should consider a lot of things like content, traffic and colors..all must come into one..they work out as a team..