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.
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.
If you want to make a clean install of the new OS X Mavericks or even the older versions of Mac OS X, than I strongly suggest you to create a bootable OS X key or a drive.
Errors on the hard disk on your Mac OS X computer can be the cause why the computer doesn't run as fast as it used to. Let me show you how to check and repair the errors on a disk drive.
You created your own movie in iMovie but you can't figure it out how to save the darn thing into a playable .mp4 file on your hard drive. I've been there, let me show you how to do that.