Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
And the functionality has been improved, which provide menu items in firefox Tools menu that has 2 functionalities:
(1) Option menu shortcut button
(2) "Theme Shuffle!" button ~ allow you to switch theme without losing your old firefox session. Shortcut key "shift+S" is provided, so that you can randomly switch themes in a much faster manner.