Forum Moderators: open
I think that you are doing the best thing you can do by keeping all of your javascript text in a *.js file. This will keep your page cleaner and google happier.
However, do not handle your links using javascript in any way. If you want to use a popup window use <a href="blahblah.htm" target="#">Blah Blah</a>.
Google will enjoy this more than a popup or any other type of link handling with javascript.
In this august forum, I'm embarrassed to admit that I'm one of that class of visitors - but if I get "assaulted" with spurious windows during a visit, I seldom return to that site.
I regard exit popunders as about as welcome as someone letting a door slam in my face as I walk to the exit. And it's especially irritating on a slow dial-up, when the user is trying to leave the site and gets bitten round the ankle by more bandwidth he doesn't want.
Oops - my prejudices are falling out!
But seriously, I find then anathema to the browsing experience and it drives me away faster than it drives google away...
So if nothing else, my advice is "make it a GOOD popunder" <smile>
DerekH