More adsense ads on one page in other way

I saw more adsense ads on some sites. Is that possible?

[ckissi]

Hello All,

I'm wondering if what I saw on some sites is legal and I can use that too. I browsed the web and found about 3 sites that use 2 adsense ads per page. I mean classical ads not combination with Adlinks. It was done by IFRAME, so the other ad was on different page and was included to current one via iframe. That different page used other keywords so the ads served by adsense were different from ads served by "mother" page. If someone has answer from google on this let us now please. I'm also waiting for every single opinion. Thanx in advance.

[Xartan]

AdSense allows you to use 3 adblocks per page:
[google.com...]

[Zygoot]

Indeed, Google allows you to use 3 Ad blocks + 1 Adlinks block

[spikedo55]

I thought I read somewhere that the more ad blocks you have, the less you earn per click. IS this true?

[hyperkik]

It has been said. It has not been my experience. However, it is my experience that each successive ad unit will have less valuable ads.