One of Safari 5's new features is an Undo system that goes beyond the basic undo function of previous versions of Safari. Sure, older versions of Safari could undo typing, but when you accidentally closed a tab, it was gone. And believe me, I have accidentally closed tabs quite often, each time eliciting a small growl of disbelief at what I just did.
Undo a Tab Closure in Safari 5
Safari 5 takes the pain out of accidentally closing a tab. When you make this common mistake, you can simply select the Safari 5 Edit menu. Instead of seeing a grayed out Undo command, you'll be greeted by an accessible Undo Close Tab command, in the same spot in the menu.
Selecting Undo Close Tab restores your accidentally closed tab and quiets those growls of frustration.