pop-under script....
That's where the new window appears
underneath your browser window, so you can't see it immediately. But it will become visible when the person closes the window....
I find them less annoying than pop-ups, personally. Are they still effective? You'll have to test and see....
I've linked below to a free pop-under script, in case you want to try it out....
- Dien Rice
Javascript pop-under generator....