What special ad implementations are permitted by AdSense policies?

Generally, altering the behavior or targeting of AdSense ad code is prohibited. However, publishers are permitted to use scripts which allow users to close the ad unit by clicking on a box. Also, to allow scrolling, publishers may place ads in a static frame while the primary content of the site is in a secondary frame.

Some examples of unacceptable modifications include:

Placing Google ads in a "floating box" in which ads scroll, hover, or expand over the webpage
Adding irrelevant keywords (hidden or visible) to alter the targeting of the ads
Using IFRAMEs with keywords to alter the content or language of the ads

 

what about a floating box which sticks to the top left of the screen for instance?

 

I think the stressed the floating box...its not allowed

 

they say static frames, but it can be a static div, if it is not over the webpage.