You deleted everything from your USB key or a drive, so there should be enough free space to copy the new files, but you still get the not enough free space message in Mac OS X? This is what you need to do.
If you are more of a visual person and would like to organize your folders and files using different colors, than check it out how to use color labels in Mac OS X.
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.
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.
We have already learned how to create a bootable OS X Mavericks USB drive using a third party app, this time I will show you how to create one directly in Mac OS X.
Mac OS X Moutain Lion and its Safari web browser sharing options allow you to share and send any web page vie email as a PDF attachment in a matter of two clicks.