I noticed that I get one single "pop-under" once for each day I get on-line.
Today, for example, the pop-under was:
http://b.casalemedia.com/V2/62428/130828/index.html?www.kmtr.com/
With the "KMTR" at the end, I was sure of the source.
While not convenient , since I have to close the window later, it won't stop me from coming to the site. I'd rather have someone else fund you site than you charge a fee for access. :-)