without violating TOS? vs.
when you don't want any visible text
these two things just dont fit together...
just put a litte text in the footer of your site or anywere where you can't see it immediately and put the following code around.
< !-- g**gle_ad_section_start -->
YOUR KEYWORD-RICH TEXT
< !-- g**gle_ad_section_end -->
i thing that wouldn't cross the border... everything else would...
things like.. putting the text in a NO SCRIPT tag...
or use <div> tag to hide it anywere.. behind pics for exemple...
it's just a metter of time till your acoount gets banned