Say that you're about to give a presentation, or someone else wants to use your computer. If you're running Mountain Lion, you may be a bit worried about what notifications may pop up on your screen. You never know when that asinine friend of yours is going to send another off-color joke, do you?
There are a couple of ways to temporarily disable all of Notification Center's messages, though, so here's how to save yourself that embarrassment. Or, you know, how you can remove distractions so you can get work done. Whatever floats your boat.
The first method is very simple. Just hold down the Option key and click on the Notification Center icon in the upper-right of your screen. That'll change the icon from this…
…to this, indicating that it's off:
The other way to do it is to click on the Notification Center icon to open the panel, then swipe down on your trackpad to reveal the hidden Show Alerts and Banners option.
You can then toggle it off from there if you like.
As you can see from the screenshot above, turning that off is temporary, as the notifications will resume automatically the next day. This is true if you use the Option-click method above, too, so if you forget to put them back on, you don't need to worry about it!
Apple says, by the way, that if you connect a projector to your Mac, notifications are automatically disabled. If I were you, though, I'd make certain that's the case before your presentation starts. Absolutely certain, even. Totally certain. No, I'm not paranoid. Why do you ask?