Vlad has given a simple tip on his Geld 2.0 website on how to improve the performance of advertising with a few CSS manipulations. In this context, performance means less the amount of revenue, which could possibly increase slightly due to the optimization, but rather the time it takes for the web browser to completely set up and display the target page. Because in many cases web browsers operate serially, stop the page construction while executing Java scripts (such as Google AdSense code) or even interrupt the reloading of other page objects (images, scripts, CSS). This leads to delays in the page layout, which can upset one or the other visitor in the fast-moving Internet or, in the worst case, cost. To counteract this effect it is better to put the script at the end of the page. How to do it the smartest, you can read up on Vlad now.
Google will probably add more to the in near future and convert to asynchronous reloading of the AdSense code. Until then, elegant tricks like this one for AdSense optimization are the best you can do. Incidentally, the tip originally comes from Aaron Peters , where you can also find the complete derivation with interesting time / sequence diagrams in addition to the tip.