If you experience an Mac OS X program to freeze and you cannot exit it by clicking quit or using a keyboard shortcut, you can always force it to quit using the Activity Monitor.
You are trying to install or open an app that didn't come from the Mac App Store but you got a message saying App can't be opened because it is from an unidentified developer. This is how you bypass it.
VirtualBox is a great free cross-platform virtualization program that enables you to run Windows, Linux, Mac OS X and other operating systems on you Windows, OS X or Linux computer.
Mountain Lion enables you to set notification alerts to remind you of upcoming birthdays, tasks, meetings and other important events you might have in your calendar.
Sometimes you don't want your Mac OS X Mountain Lion powered computer to go to sleep, here's a nice little trick how to temporary prevent a Mac from going into a sleep mode.
