gui:config makes it easier to change preferences that can only be found in the “about:config”. The extension supports a comfortable way to apply changes to these options. It displays the options, included in the current version, using checkboxes, dropdownlists and textboxes.

For a short introduction go to http://blog.freedig.org/guiconfig/first-steps/

Thanks to the people at babelzilla.org for the translations.