New in Mountain Lion is the Notification Center. Carried over from iOS 5 (operating system on the iPad, iPhone and iPod Touch), it is a central location where you can view your notifications, events, alerts and reminders. To display the Notification Center, click the small three-lined icon on the top-right corner of the window. A new panel on the right side of your screen appears, displaying any notifications that are waiting. These can include calendar events, e-mail alerts, Twitter and Facebook alerts and/or mentions, events & appointments from the calendar app and reminders/to-do’s from the Reminders app.

To view any item in the pane, simply click it in the Notification Pane. This will display the item in its associated application. All notifications are sorted by application. To remove all notifications for a particular application (with the exception of Calendar – its events disappear automatically after the date passes), click the x next to the application’s name.

If you have added a Twitter or Facebook account from the Mail, Contacts and Calendars area of the System Preferences pane, you can send updates directly from the Notification center. Simply click Click to Tweet (Twitter) or Click to Post (Facebook) and type in your Tweet or Facebook status update in the box that appears. You can also add your location to your update, if you so choose.

You can access the settings for the Notification center by either clicking on the settings icon in the lower right corner of the Notification Pane or by clicking Notifications in the Systems Preferences window.

From the Notifications System Preferences pane, you change the behavior of notifications for each application in the Notification Center. One of the properties that you can set is to change the alert style. There are three styles you can set: None – You will receive no alert on your screen at all. Banners – A banner alert briefly appears on your Mac screen but will then disappear after a moment. You can still find the notification in the Notification Center Pane.

Banners stay on your screen only for a few moments

Alerts – A message box appears on your screen and will remain there until you press either the Close or Snooze button to dismiss it.

Alerts stay on screen until you press a button

You can also choose the number of notifications that will appear in the Notification Center for each application, whether to display a red badge icon next to the app and whether to play a sound when you receive a notification.

If you will be away from your computer or don’t with to be otherwise disturbed, you can turn off all alerts and banners. To do so, scroll to the top of the Navigation Pane and swipe the Show Alerts and Banners button to the Off position. No alerts and banners will display for 24 hours.

To Set Notification Center Preferences

1. Click the System Preferences icon on the Dock. Or Select  > System Preferences from the menu.
2. Click the Notifications icon under the Personal area.
3. In the left pane, click the name of the application you want to modify.
4. In the right pane, choose None, Banners or Alerts.
5. Click the drop-down list next to Show in Notification Center and choose how many notifications for that application you wish to display.
6. If you wish to include the Badge App Icon, click the check box to select it.
7. If you wish to play a sound when receiving a notification, click the check box to select it.
8. To display the Notification Center, click the small three-lined icon on the top-right corner of the window.
9. To remove all notifications for a specific app, click the x next to the application’s name.
10. To turn off all alerts and banners for 24 hours, scroll to the top of the Navigation Pane and swipe the Show Alerts and Banners button to the Off position.