Configuration Mania is a Firefox 2 & Firefox 3 add-on that organizes and displays many of the advanced (hidden) configuration options that are normally only available through about:config. Here are just a few o the things you can change using Configuration Mania:

• Location bar auto-complete behavior
• Default domain guessing behavior (should Firefox add www or .com when you type a word into the location bar?)
• Tab behavior (where to display the close button, default tab width, etc)
• Hide the Go button next to location bar
• Change your user agent
• Adjust cache settings

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Firefox, Firefox 3, Addon, Add-on, Extension