if you go to
http://www.cooterville.com on your first click in a window will launch to sexier.com and go under in IE. In FF it should open in a new tab but the focus should remain on the main tab.
After the first click the site should behave normally.
Just using a little css with a touch of script but none that most popup blockers I know of would notice. There is a transparent image across the entire page with an href attached that opens in a new window using target=_blank.
There is an onclick event that hides the transparent gif so the main page will be usable.
Then on the page that is launched there is a self blur line of script in the header so it puts itself under, or in the case of ff loses focus on the new tab that was opened.
Took about 10 minutes to put together and test.
Watch out. I have it in the footer of the theme so right now it will reload the transparent gif every time you go to a new page and therefore you will get another popunder if you continue to click around and on and on and on.
Gonna go into the template and fix that.