I've done some checking for you I.E types.
There is no chance of pop up blocking until XP's Service Pack 2 and this is scheduled for 'the summer.'
For Mac users Microsoft has halted any development of I.E - this was announced several months ago but at least you have a raft of well supported alternatives.
For PC users you'll have to stick with third party tools whether executable software or one of the add on toolbars from folks like Google.
Alternatively you can opt for one of the modern highspeed browsers with tabbed windows. Here at the Towers we've made it clear which option we suggest for getting the most out of the site.
One final point, especially if this thread becomes part of an FAQ. If you are running software that blocks pop ups and you find some parts of PPRuNe are missing it's down to the software/settings on your machine. Most common occurence is for 'reply' or 'new topic' captions to disappear but many and varied are the effects!
Regards
Rob Lloyd