As of Firefox 1.5, the popup blocker can be easily be escaped or overridden. The popup blocker works on the principle of blocking popups that spawn without any interaction of the user.
To override this, what is done is add user interaction (unknown to the user…) to spawn a popup.
All you need to do is add an EventListener… to particular area of the page which is viewed, read and make a popup.
I’ve written more, with the code… at the following URL, Spawning popup windows in Firefox