I didn't go to any great lengths to try to discover the precise circumstances under which it happens, because even one time is one time too many, but What Is My IP occasionally brings a dreaded and dispicable Flash pop-under along with it. I suggest Speakeasy, which offers an 8 city selection and which I have found yields comparable, pop-under-free results.
The new Great Equalizer is the SEND button.
In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire
I suggest 