Would a small pop-under be a violation of Google adsense? https://www.google.com/adsense/supp...ceid=asos&subid=ww-ww-et-HC_entry&medium=link Sites showing Google ads may not contain pop-ups or pop-unders that interfere with site navigation, change user preferences, or initiate downloads.
I'm of the opinion that any type of pop-up interferes with navigation, but luckily I don't work for AdSense. That said, I'm sure some of them will think the same so it depends on who reviews your site. I would ask them for an opinion.
I only have a pop-under. Could it be "illegal"? It's not upsetting the visitor and it does not interfere with my page which contains adsense.
It's probably okay. Pop-ups, pop-unders, pop-whatevers - they're all the same to me. If I find a site with them I don't go back. I think they're an offensive way of inflicting advertising on your visitors who have no choice but to endure them.