When you accidentally close a tab in Firefox, the Ctrl+Shift+R combination can really save your life, bringing up the last closed tabs. You might be wondering if there’s a more comfy way of doing this, and in fact there is.

Photo Credit: Martin Jans - Edit Nicolo’ Canali De Rossi

Undo Closed Tabs Button is a Firefox add-on that you can use to actually browse the history of your recent closed tabs.

After you install it, you must add the toolbar button by going to View>Toolbars> Customize, then drag and drop the icon where you want it on the toolbar.: everytime you click that button, the last closed up will open again, like if you were pressing the Ctrl+Shift+R combination but, if you click the little arrow next to it, you will be shown the actual history.

You can personalize the extension deciding how many tabs it’ll keep in memory (up to 99), which buttons to show (tab bar button, right click menu) and whether to remove the history from the button.

Link: https://addons.mozilla.org/en-US/firefox/addon/3082