Where it's said? It's allowed As I know at least I have also in that place, You can't put them near to images what actually links to that ads. Than only you will brake their TOS
You basically can't put them in places that makes it look like they need to click on the ad as part of your site. You can not use images to entice people to click or make it look like the ads are sponsoring your site. The biggest no no is outright asking them to click on your ads.
Right, the terms and conditions (section 5) says "You shall not, ... (v) display any Ad(s), Link(s), or Referral Button(s) on any error page, on any registration or "thank you" page (e.g., a page that thanks a user after he/she has registered with the applicable Web site), on any chat page, in any email, or on any Web page or any Web site that contains any pornographic, hate-related, violent, or illegal content;"
That is if it is on a page made just for registration not if it is next to an area where you register. You can not have just a registration page with no other content on it or a thank you page after your register.
that is true. they dont allow you to put ads on such pages. If they find out they will disbale your account.
Yea, it goes back to the basic rule in my eyes: don't put Adsense ads on pages that have no real content or "value". I don't consider thank you pages or registration pages content pages at all....