Tired of new windows opening when you click on a link?

Solution 1

Open about:config and set browser.block.target_new_window to true. All links that are target to a new window will open in the current browser window in the current tab.

Solution 2

Open about:config and set browser.tabs.opentabfor.windowopen to true. All links that are target to a new window will open in the current browser window in a new tab.
CAVEAT: Solution 1 takes precedenc over Solution 2 if both are set to true.