I used to have a custom about:config setting that made it so that any popup a page would generate was opened in a new tab instead.
With my new install, I can't remember the name of this setting. Can anyone help me out here?
I can't tell you the name of the setting, but you mention having a "new install." If you are trying to configure firefox on a new machine, or if you think you will have to do this in the future, I highly recommend this little java applet. It is an absolute gem. Forget importing bookmarks and any reconfiguration. This program will take your entire firefox profile and convert to a format which it will later use to import to your new machine.
Hope it's at least a little help for the future if not right now! ;)