ok there was last time I set up adsense but heyho, a quick search on the adsense support, which of course would be THE place to look and you would have had an answer in about 0.5 of a second
OK, thanks for your info.
But I have a further question: if my adsense codes is in an iframe, then what is the referral URL detected by it, the top page URL or the referral URL of the top page?
Chris' second link says: The AdSense ad code should be placed within the frame containing the content you wish to target with the ads. This means that ref is the framed page.