I have two questions about Adsense When two ads are shown on the same page,do they show advertisers from highest to lowest bid on the first ads and then the same advertisers in second ads ? Will it affect the price per click if i implement one or three ads on the same page ? More impressions lower prices (smart pricing)
The term for this is not smart pricing, but generelly yes, the more ad units you choose to display per page, the lower the avarage cpc will be in my experience. To avoid this happening you might want to ensure that your unit which gets the most clicks appears first in your source code (regardless of whether it appears first on the page).
Smartpricing has nothing to do with your impressions, it's all about how well the clicks you GET converts for the advertiser.
But hey, the less ads you display on your site, the lower your CTR would be So which way should one go
No. Google displays ads based on CTR * CPC. So whichever ad would make the most revenue in the long run gets displayed first. The same advertiser will not be shown in the second ad unit. The same CTR * CPC formula applies to all the ad units, starting with the one that appears first in the HTML. So if you have two ad units each with 4 ads, the top eight ads according to CTR * CPC will be shown.
I have seen many times duplicate ads by the same advertiser in multiple units. e.g. same ad in the last ad of the first unit and first ad of the second unit. I wonder why?
No, you don't bid for spots in AdWords, you just set one bid price and AdWords figures out what spot to put your ad based on CPC * CTR. One possibility is that an advertiser had two separate campaigns going, so each campaign got a spot? I'm just guessing here.