1. can smb tell shortly how referals work? how many can i place in my page? 2. should i notify google if i add my ads in another site? Thank you. This forum is helping me too much. Great!
As long as your ads go along with the TOS (porn ect) there should be no problem with adding your adsense to any site.
Don't forget to make use of the URL channel feature so you can keep track of individual site impressions and clicks.
You can place 2 referral units on any "one" webpage, each unit can have multiple referral offers that rotate or are displayed together. You don't need to notify them about any new sites you add AdSense ads to, just make sure they are compliant with the current standing TOS.