Thanks,but i have read that google bans the site if anything else than adsense is used and adsense allow only three ads
you read wrong. you could always use other networks along side adsense. they say this... adsense has "Ads by Google" and YSM has "Ads by yahoo". as long as the other network ads are within googles Content Guidelines,i wouldn't worry about it.at most they will ask you to remove the other network,but i haven't heard of them doing that. i would read yahoo's TOS. it's use to be that yahoo didn't allow any other network.i don't know if they changed that.