Almost every Mac OS X application allows you to customize its settings. These settings are saved in a Preference file. Because Mac OS X allows multiple users, an application will save your Preference file in the Library folder for your user name. To find it, look in /Users/[username]/Library/Preferences/.
Preference file names begin with “com.” and end with “.plist”. In between is the developer’s name followed by the application’s name. For example: com.apple.TextEdit.plist or com.adobe.Photoshop.plist.
These are the Preference files to throw away when an application misbehaves so badly that a technical support person suggests you “trash its preferences file”.
A while back, I wrote another story about where QuarkXPress keeps its preference files, and where you should store yours: “Quark’s Preferences Folder: Where Should It Live?