I have seen more than 3 ads (display ads) on one page, some people suggest that when used with programs like chitika etc, you may have upto 4 of them (when chitika premium is not available for countries other than US / UK, etc., it replaces their ad with your adsense code). Tell me if this is possible...?
you have to add script codes of the ads and its adsense policy to not show more then 3 ads on web page. so if you try to put adsense codes at 4 places on a webpage it automatically will show only 3 ads units and if you use chitika so when it will not available, it will replace with adsense codes so it will also show onlye 3 ads units. you can't put adsense codes in iframe but iframe can show ads as much you want but its against the TOS, i have got warning on this while showing ads into iframe in the beginning, so don't do it. but you can put adsense for search with 3 ads units. good luck
It is against adsense TOS and you will get banned. So, what is the point to put 4 ads block? 3 is more than enough
Definitely against TOS, they don't allow more than 3 blocks in any way.. so it doesnot matter if chitika is not showing then google will allow 4th block on the same page where you have already been using 3 blocks