The update to Mountain Lion is for Developer Preview 3, and adds a new “Do Not Disturb” feature for notifications, reports 9to5Mac. The new feature allows users to quickly toggle Notification Center alerts and banners on or off. This feature is particularly useful for those who don’t want to be distracted by Notification Center alerts.
To show that the Do Not Disturb option has been switched on, a moon-like logo appears in the top right corner of the screen, next to the spotlight icon in the menu bar.
It is possible that Apple will decide to add the Do Not Disturb feature to iOS 6, the next version of its mobile operating system.
Apple also seeded a new build of OS X Lion 10.7.4 to developers. Apple says that when using the new build, 11E53, developers should focus on testing graphics, iCal, Mail, Printing and Time Machine.