Working with the Library Folder in Mac OS X Lion
The Library folder, at the root level of your Mac OS X Lion hard drive, is like a public library; it stores items available to everyone who logs into an account on this Mac. You can find three Library folders on your hard drive: the one at the root level of your OS X disk, a second inside the root-level System folder, and a third in your Home folder.
In earlier versions of Mac OS X, you would have seen a folder named Library between the Downloads and Movies folders in your Home folder. But that was then, and this is now. In Mac OS X Lion, the Home Library folder is hidden from view to protect you from yourself.
Leave the /System/Library folder alone. Don’t move, remove, or rename it, or do anything within it. It’s the nerve center of your Mac. In other words, you should never have to touch this third Library folder.
You find a bunch of folders inside the Library folder at root level (the public Library folder). Most of them contain files that you never need to open, move, or delete.
By and large, the public Library subfolder that gets the most use is the Fonts folder, which houses many of the fonts installed on the Mac. For the most part, fonts can be made available in one of two ways:
To everyone who uses the Mac: If that’s the case, they’re stored in the Fonts folder.
To a single user: In this case, you place the fonts in the user’s Library folder (the one in the user’s Home folder).
Some other public Library subfolders that you might use or add to are the iMovie, iTunes, iPhoto, and iDVD folders (where you put plug-ins for those programs); the Scripts folder (which houses AppleScripts accessible to all users); and the Desktop Pictures folder (where you can place pictures to be used as Desktop backgrounds).
Leave the “public” Library folder pretty much alone unless you’re using the Fonts folder or know what you’re adding to one of the other folders. Don’t remove, rename, or move any files or folders. Mac OS X uses these items and is very picky about where they’re kept and how they’re named.
If your Mac is set up for multiple users, only users with administrator (admin) privileges can put stuff in the public (root-level) Library folder.