repeated ads on 2 or 3 ad units

do I have to set something for multiple ads

[annej]

I thought I'd experiment with three small ads scattered througout the page instead of one long tower. I seem to be getting an occasional repeated ad on the same page though. Does that happen to everyone or is there something additional I need to do to be sure ads don't repeat on the same page?

[TNJed]

your site theme may be in an industry where there just aren't enough ads to support 3 full ad blocks.

I wouldn't recommend it though. For each additional ad block you add to a page you lower your potential CTR by 50%.

If you have 3 ad blocks on a page for every click-through you register you register 2 no-clicks on your other ads. This will effect your EPM.

[annej]

Do you mean it's like each person visited the page three times instead of once?

Three ads with two each is only one more ad than the large tower.

[TNJed]

If you visit your page one time, it registers 3 impressions because of the 3 ad blocks. If that visit results in a click your CTR is 33%. That's the highest CTR you can get. If you only had one ad block you'd be at 100% instead. With 3 ad blocks you are effectively starting a page off with a ceiling CTR of 33%. My target is usually 33%.

Speaking of percentages, I'm not 100% this is how it works but from what I've experimented with, it's what I saw.

I added 2 more blocks to my pages once. My impressions tripled, my CTR dropped by about 70% but the number of clicks remained the same. So, the wheels were spinning but I wasn't gaining ground. In fact, because of the lowered CTR my EPM was also less so I earned less. Once I reverted back to the one ad block my numbers bounced back. Anyone with a similar experience?

[annej]

Oh Lordy, I think you are right. I just made less than a dime on two clicks.

It's back to one ad.