Ever wanted pages to open up in a new tab instead of opening a whole new browser
in Firefox?

Type about:config into the URL, hit Enter, scroll down and find the value browser.tabs.opentabfor.openwindow, change the value to true. Then
right click in the window and select New -> Boolean, call the value browser.tabs.showSingleWindowModePrefs
and set it to true.

There will now be a new set of options in Options
-> Advanced -> Tabbed Browsing. Check the box for Force
Links That Open New Windows and then choose the sub-option that suits you.

You will need to restart FireFox for the settings to take effect.