remember when I first tried Opera, that was supposed to be “the fastest browser on Earth”, I accidentally pressed a mouse button combination and weird lines started drawing through the screen. The mouse gestures (I was to find out about them later) are stylized motions of the mouse cursor itself, that can be used as forms of commands and that can be mapped to a specific action. For example, you could have quickly moved the mouse towards the left direction to go back to the previous page.
At that time I was still using Internet Explorer and new features like tabbed browsing or cached pages seemed like heaven. I started using Firefox since one and a half years ago, and I of course I sticked to it until now. With the discovery of widgets that are able to completely transform Firefox now, it does seem like the best browser on Earth for me, not necessarily the fastest.
However, I did not see the gestures feature being implemented in the core system, so I thought there might be a Plug-In to do so. Here it is. The extension allows you to execute common commands (like page forward/backward, close tab, new tab) by mouse gestures drawn over the current webpage, without reaching for the toolbar or the keyboard.
You can also use click-only “rocker” gestures which are even faster than drawn gestures. This cool plugin is compatible with your Thunderbird aswell.