This one is a real time-saver for me.
In Google Chrome, there are times when I have an important tab up--say, with a map showing the directions to a meeting or a website I found after searching forever.
In Chrome, if you get too many tabs open at the same time, it's easy to click on the tab but accidentally click the x to close it instead. Poof, that website is gone. In the past, I've had to check my history or try to remember what was in that tab. However, there's a neat trick to restore the tab instead. Just press Ctrl + Shift + T and it will magically reappear.
Mac users, it's Command + Shift + T.
A side benefit is that the restore tab command, which is also available in the menus, also brings you to that tab so you can see what you lost and get back to work.
I found this keyboard shortcut online recently (sorry that I can't remember where it was), and tweeted out the tip. Several dozen people hit retweet, leading me to believe this is a common problem. Of course, you may know that, as you create more and more tabs in Chrome, they get quite small. One of my editors has shared his screen before and he has up to 20-30 tabs open at once! When you do that, it's even easier to accidentally close a tab because there's a tiny area where you can click the tab right next to the close check.
Most browsers these days have a restore tab feature. In Firefox, it's a menu option when you right-click on a new tab. Just look at the menus and memorize the key command shown for restoring. For example, in Safari, it's even easier than Chrome. You just press Command-Z to undo the tab closing (undo works in most Mac apps).
Here's another trick I use quite often.
Because it's so easy to pull up a lot of tabs, which leads to some confusion over where you have them and why you even opened that tab, I sometimes use a totally different process. I'll find a site I want, but instead of keeping the tab open, I'll click and hold down on that tab, then drag it away to create a new window. This helps keep things a little more organized because it's no longer just another tab, and I know it was important enough to make it a new window.
There's another advantage to doing that--since Chrome maintains memory for each open window as though it's another app, if your main browser window with a bunch of open tabs were to crash or you close the entire browser window by accident, that other window won't close. Fortunately, Chrome will restore all tabs automatically after a crash.
By the way, if you use this tip for restoring tabs, can you let me know on Twitter? I'd love to spread the word about this one if it helps people be more productive.