Eleven hot tips for making money with google. Tip 10
Where should I place Google ads on my pages?
Certain locations on the page are ?hotter? than others. In the accompanying image (below), we notice that the colors fade from dark orange (strongest performance) to light yellow (weakest performance). Also, ads placed above the fold tend to perform better than ads placed near rich content and navigational bars because users are focused on those areas of a page.

Always put your users first when deciding on ad placement. Consider how they will navigate the page, and what will be most useful and visible to them. Sometimes this will call for the ad to be placed other than where expected.
Tip number eleven to follow. If you want to advertise your website for free then have a look at goFreeClick free text ads.