If you leave applications running without any open windows, Mac OS X will quit the application when it goes to the background. There is no setting in the system preferences to change this behavior. Use the following command to disable automatic application termination.
10.8
Keep full screen mode in Quicktime when switching applications
When you are watching a video in QuickTime’s full screen mode and you use cmd⌘ + tab to switch to another application, the movie will automatically exit full screen mode. To stay full screen in the background, use the following defaults write command:
Re-enable the delete key (page-back) in Safari 6
In Safari 6 the behavior of the delete key has been changed. If want to return the ‘page-back’ navigation behavior to the delete key, you can do so with the following defaults write command.
Re-enable the repeat key feature
When you press and hold a key in Mac OS X Lion or Mountain Lion, it is no longer repeated. Instead, an auto-correction pop-up would appear, allowing you to select accented characters. This default write command will re-enable the repeat key feature.
Display only active application in the Mac OS X Dock
If you prefer a minimalist Mac OS X Dock, set the Dock to only display active running apps.
Change the frequency of software updates checks
Mac OS X 10.8 Mountain Lion removed the ability to set the frequency of checks for software updates. The default frequency is 7 days, use following command to change this:
Enable AirDrop in a wired network and old Macs
It is possible to enable AirDrop in a wired network even when your Mac is not supported. After restarting the Finder, Airdrop will appear in Finder’s navigation bar.