On February 2008 I wrote an article how to improve earnings from PPC ads by better ad placement. If you happen to miss it here is the link for you http://www.cosmocentral.com/post/Earn-More-with-Better-Ad-Placement.aspx

I actually made most of those changes on my site webcosmo.com. This is a follow up writing to let you know what happened. To be honest I actually was surprised myself seeing the results. Literally my AdSense (thats what I use on that site) earnings doubled since I have made two changes.

First change I made is, I have put the ad on a nice rectangle on all the ad listing and details pages. Idea was blending the ad with the site design so it does not look like a foreign object. This improved the earnings by about 10%. This ad block was residing at the top of the page content block.

Second change I made after a week of the first change. I put an additional ad block at the bottom of the page content block on each ad listing and details pages. Reason I did this is, if a user goes to the end of the page reading through the content its the best place to have an ad block catch eyes of the visitor. That made the magic. Earnings improved a lot.

I personally prefer not to destory the look of the site by placing ads everywhere. Keeping it nice and clean is my formula. Don't put ads everywhere saying "click me, I need money". Main purpose of any website should be serving the content/service to audience. As long as you enjoy serving people money will come on its way.