Hiding description text

i visited this site

from a signature and it is using YPN and the description is hidden using the same colour as background can we do it with adsense.

 

You are not allowed to obscure any part of Adsense ads.

 

I bet his making tons of clicks with that.

 

great tricks.i was just thinking of making the url of same color as that of background.but first would like to learn adsense rule against this.i mean is it against adsense toc to hide url or description.