I honestly wouldn't have known the difference, since I have
unauthorized (un-initiated by me) popups disabled on Mozilla.
If that popup has some critical information, you should
probably take that into consideration. I personally find
popups annoying, (which is the main reason why I started using
Mozilla in the first place) but now I never see them. You
might want to consider doing something else on your page
rather than a popup. While I don't necessarily think
that its one of the top 10 ways to make sure they don't
come back, I think its definitely up there with flashing
text, music, and badly-coded frames. (I don't mind music that
I can click on to play, but I dont want to be surprised when
I click on something and have music blaring all of a sudden)
Just my thoughts,
MG