Notifications Center is a quite handy feature in Mountain Lion that alerts you about new emails, calendar reminders, and notifications from other apps like Facebook and Twitter. It can be very useful, but sometimes you just want to take a break from it.
This can be without too much hassle; however, most users aren’t aware of this option.
How to temporarily turn off notifications in Mac OS X:
1) Open the Notification Center by click on the icon in the top right of your screen or two-finger swipe at the right edge of your trackpad (if you are using a trackpad).
2) Now use your mouse or trackpad to scroll up, and you will see the option to turn off “Show Alerts and Banners”.
3) Simply click on the “On/Off” button, and the Notification Center will be turned off for one day.
Tomorrow, your notification bar will continue to function normally. There is also a simpler way of turning it off, now that you know how it works. Simply hold the option (alt) button on your keyboard and left click on the Notification Center icon in the top right corner of your screen.