On one site recently I was only utilizing one content ad and one link unit. I had enough content and decided to ad another content ad in the middle of the page. The ad in the middle of the page received only about 1/3 as many clicks as at the top of the page which was expected. What wasn't expected is that it seemed to carry the higher cpc ads. The ads at the top of the page cpc dropped about 60%. The result was a drop in earnings. Therefore, I
changed out the ad unit in the middle of the page for a link unit. I expected that would restore the cpc of the ad at the top of the page. But for the last two days that ad's cpc is still down.
Any thoughts as to the cause? Is it just a complete coincidence? Should I remove the link units or give it some more time to see if it will jump up again? Thanks for the comments.