I'm a little concerned. All three of the ad blocks (1 leaderboard, 1 tower, 1 300x250) on my site are taken by the same advertiser with slightly different versions of the same ad. I'm just concerned that people will look at the ad, not be interested, look at another ad, not be interested again... basically that it will hurt CTR If there any way I can block the advertiser from monopolizing my site? or is it all or nothing?