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.
Mac OS X Mountain Lion has 43 secret desktop wallpapers hidden in one of its folders. They are all beautiful, high quality and this is how you find them.
Photograph files taken with a digital camera also carry certain Exchangeable Image File Format (EXIF) data where you can see the camera settings that were set when the photo was taken.
If you find yourself in a situation when you need to list your Mac specs or you just want know if you really got what you paid for, this is how you find them out.
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.
You can add multiple desktops to the Mac OS X Mountain Lion by using Mission Control, formerly known as Spaces. Can be really useful if you are a busy multi-tasker.
