Find your configurations files. There are configuration files for Firefox and for the user. User configuration files are in the user's profile, while Firefox default configuration files are found in Firefox's defaults folder.
Each operating system family stores configuration files in a different location. You saw how to find your user configuration files, and where the Firefox default configuration folder is.
Firefox global preferences and properties are used to hold preferences for all users, and to initialize a new profile's preferences.
Defaults.ini and components.ini are used to tell Firefox to load additional configuration files. Use this option to add your own global configuration changes.
Creating and editing user.js allows a user to set the highest priority preferences. Everything in user.js overrides settings from all other sources.
Cascading style sheets are used to control both the look and feel of web pages, as well as Firefox's user interface. Cascading style sheets are standardized and substantial documentation on them is available on the Internet.
userChrome.css and userContent.css control the look and feel of Firefox, and the default look and feel for a web page.
You can use themes to change Firefox's look and feel, much like other programs use skins. Themes modify userChrome.css, userContent.css, and other configuration files.
Flexbeta FireTweaker is a powerful tool to improve Firefox's performance, look, and behavior. FireTweaker is a standalone program, not an extension.
ChromEdit is a user profile editor. Although you may edit userChrome.css, userContent.css, user.js, and prefs.js yourself, ChromEdit makes the task a bit easier.
Many additional browser performance improvements were covered in this chapter, including pipelining and rendering tweaking.
Along with everything else, the preferences that affect performance are described fully, with default and recommended values for most.