piatkow - 9:25 am on Feb 22, 2013 (gmt 0)
It is well known that many users are reluctant to scroll at all. If your ads are just on "the fold" then the fact that the ad is there may just be coincidence.
And even when information is on the page people still don't see it. I used to have a site with my real world contact details, people would phone me to find out the postal address despite the phone number being printed UNDERNEATH the address.