In our articles, we often mention the about:config command which can be entered in the address bar. That command opens the built-in configuration editor of the Firefox browser and allows performing extreme fine-tuning of the browser. It contains lots of options which are not accessible from the browser's settings interface. Many Firefox users are not even aware that about:config is not the only about: command available in the browser. Firefox comes with a huge set of useful about commands which I would like to share with you today.