Adsense in iframes

What are the legalities of this method?

[progex]

I've seen many sites that display their Adsense in iframes in order to correlate more relevant ads to the page's content.

Does this break Google TOS?

[Staale]

No it do not break the TOS. Here it what Google says about it:

"If your page uses Frames, make sure that the code is pasted into the frame that contains your page's main content. We use this content to target ads"