In Firefox versions prior to 4.0.1. I used to be able to simply click on one of my middle mouse buttons to close the current tab. This feature no longer works in version 4. Now the mouse button closes all tabs. The only other ways I have found to close current tab is either move the cursor to the X on the tab and click it, or to use the keyboard shortcut ctrl+w. These methods are more cumbersome than simply clicking the middle mouse button from anywhere in the tab. How do I setup this feature in Firefox 4? Thanks.