Mountain Lion's Notification Center is handy. It displays banners and alerts from notification-aware apps to keep you informed of changes, like a new Twitter mention, Calendar event or email message. That last one can get distracting, depending on how much email you receive. Here are some ways to tame email alerts:
- Disable alerts and banners in System Preferences. Open System Preferences and click Notifications. Select Mail from the list on the right and then click None. You'll no longer see email notifications.
- Quit Mail. Apple's Mail app won't push notifications if it isn't running.
- Turn them all of at once. Open Notification Center on your Mac and swipe up to the very top. Move the slider labeled Show Alerts and Banners to the Off position to silence all pop-up alerts and banners (they still appear listed in Notification Center itself). Slide it back to On to restore alerts and banners.
If you're worried about a notification popping up when you're making a presentation, don't be. Notification Center is smart enough to recognize when you've got Keynote open and silences notifications on its own. Additionally, it won't display alerts or banners on a mirrored display.