Oops! Undo

Have you ever accidentally closed a tab while you were browsing on the internet?  To reopen the most recently closed tab and get back to what you were doing: 
On a Windows computer, simply press Ctrl + Shift + T
On a Mac computer, press Cmd (Command) + Shift + T 
Another "undo" key combination to remember in case you accidentally erase words in your email or document as you are writing it:
Windows - CTRL + Z
Macs - Cmd (Command) + Z
These keyboard shortcuts have been timesavers for me the past couple of weeks when I've been shopping online!