Settings to improve Firefox.
This is my take on settings that help make Firefox better. See dfkt/firefox-tweaks and pyllyukko/user.js for similar projects.
To enable these settings, copy the user.js file into your Firefox Profile and restart Firefox. Learn more about Firefox Profiles and the user.js file. Research each preference, and comment out ones that you don't want to change.
On GNU/Linux, your Firefox Profile will be in a location something like: ~/.mozilla/firefox/zxcvbnm.default.
Alternatively, you can individually modify these settings by typing about:config into your address bar, but the method of putting your preferences in user.js will make them easier to manage.