When using Firefox sometimes I like to use certain websites that have pop up windows. I don't like having multiple firefox windows open so it is a lot easier and fits with my sytle.
It is really simple as always most things in Firefox are easily changed in about:config.
Ok so it is simple, go to about:config.
browser.link.open_newwindow = 3 browser.link.open_newwindow.restriction = 0
After that all windows will be forced into a new tab instead of a new window no matter what. At least in my experience so far.