How to re-open closed tab?
Right-click on an existing tab and select Undo Close Tab
.
The keyboard shortcut is the same: Ctrl + Shift + T. (Mac OS X it's ⌘ + Shift + T.)
If I click the "Firefox" button I can still navigate to History > Recently Closed Tabs.
Al Everett is correct. If you are looking for the shortcut in a Mac OS X system, it's command + shift + T