This is hard to believe that it really works: a) For all these tracking scripts acompanying each ad it should be trivial to detect that the window is invisible

This is hard to believe that it really works: a) For all these tracking scripts acompanying each ad it should be trivial to detect that the window is invisible and really nothing is even hovered b) For everyone it should be easy to detect that a page that was loaded in the background redirects after a short time. It should be so easy to find these pages manually and ban them. Why does such an obvious and primitive technique like popunders with auto-redirecting "webrings" even work at all???