I read somewhere on some blog that if you have one site with Adsense performing very poorly (low CTR), it can affect all the other sites you have in your account resulting in lower earnings overall. As I can remember, site said that Google will tend to display expensive ads on sites that have a good click through rate. Now the question would be: Is that limited only to sites/pages or to entire account? I hope, just a rumor. True or false? Opinions or even better experiences. Damn, I can't remember that blog name.
I have noticed that if i have a site and the ctr and amount of clicks increase so does the ppc after a few days. This is site specific not for your whole acount.
well i have 3 sites, i experiment with them one site is popular and rest small unique visits my conclusion is , put ads on all pages images above the ads make ctr bigger but google wrote to me that this is forbidden you must make the clicks many.... the way to do that is put many ads with good placement the best thing is get the ads that is 100% about the content of your page that people click them the end for now