Ever close a webpage, then wish you hadn’t? In Firefox there’s a shortcut that undoes a tab close: “Shift Control t”.
Ever close several webpages in a row and wish you hadn’t? You can use the same shortcut to get back the last few pages you closed at once, e.g. “Shift Control t Times 3”. Here are some related commands: use “Document Close Times 3” to close tabs and “Control t Times 3” to open blank tabs.