This tweak is for those sites that still force your browser to open a new window. That behavior is too IE for my taste. In any case, you can always set Firefox to open these links in a new tab. It’s pretty easy to do from the interface, just click Tools -> Options -> Tabs and you’ll see there an option “New pages should open in:” and lets you choose between a new window or a new tab.

Unfortunately if you set this in a new tab, it takes the focus away and brings you to the new loading tab when you click on such a link. I really don’t like having my focus diverted immediately. Good thing you can always configure Firefox to load it in a background. Here’s how:

• Access the about:config page.
• Find the browser.tabs.loadDivertedInBackground preference name
• Double-click on it to change the boolean value to true
• Close the about:config page/tab
• The changes take effect instantly

Via Lifehacker