Use Property List Editor to Edit plist Files in Mac OS X for Free
Property List files, or more commonly known as plist files, are basically Mac application specific preference files. They contain information and settings for various applications and are usually in the easily identifiable format of com.developer.Application.plist and located within the /Library/Preferences/ directories at the system and user level.
If you simply want to view a plist file, you can give it a glance with Quick Look, but what if you want to edit a plist file on the Mac? To properly edit and modify plist files in Mac OS X, you’ll want to get a dedicated app to do so, and fortunately Apple offers one such application which allows for easy safe editing and saving of plist files.