Mac 101: Notification Center
Notification Center in Mountain Lion provides you with an elegant and unified view of new stuff that pops up on your Mac from third-party apps, Mail, Calendar, FaceTime, Game Center, Messages, Reminders, and updates from the Mac App Store. You can access Notification Center from anywhere, anytime, including full-screen apps.
Notification Center
To show the Notification Center, either:
Click the menubar icon() in the upper right of the menubar.
On a trackpad, two finger swipe left from the right edge of the trackpad.
In Notification Center, you can view your most recently added items.
Click an item to go directly to the associated app.
Click the "X" icon () on the right of the app bar to clear all items related to that app.
Tip: On a trackpad, swipe down to expose the Show Alerts and Banners switch to quickly suspend or activate Alerts and Banners. Note: If you connect a projector to your Mac, Alerts and Banners are automatically suspended.