Google generated some thing called heat maps for ad placement. Optimum placement according to the map will ensure maximum clicks to the ads
This is the link to google heat map normal version
http://www.google.com/adsense/suppor...n&answer=17954
The link below is an extended version of the google heat map which gives information on pages that are longer than one screen height. It is a bit complex one though interesting.
http://www.vaughns-1-pagers.com/inte...-heatmap-2.htm