what is the best way to change the keywords for a website which i already have high traffic ? i don't want to lost the SERP ranking.. by adding a lot of non revelant keywords. but need to show ads for high paying keywords i know it will get less CTR than normal.. the comment codes like Google_ad_Section_star,etc ? any ideas please.. thanks.
You can't change adsense keyword, you just can filter irrelevance ads. what kind of traffic it will attract what kind of ads.
https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=23168 You can use section targeting.