While I know that site ads in google go through the same auction process as contextual ads, I've noticed that site ads have a much lower eCPM on my sites. Is this normal? And if so, why don't more people do site specific ads? The official explanation from google just doesn't explain enough: Also, can you really tell what someone has bid to advertise on your site this way short of bidding on your own site (which I would find immoral and foolish and give google a good reason to ban you)? The Ad unit impressions may skew your numbers on eCPM, but I don't know how to unskew them.