Ever wondered why Firefox in Windows does things differently than Firefox in Linux? Well I don't But it is a fact that some of the Firefox default preferences in Linux are different from what you are used to in Windows. One such difference is the middle-mouse click on a tabbed window. In Windows, this closes the tabbed window; in Linux, this will paste the current clipboard contents into the Location bar and visits the site - if it is an URL - or performs a search otherwise.
Now, I want my Firefox always to close the tabbed window when I middle-mouseclick the tab. The solution:
~/.firefox/default.<some_string>/user.js
. Add this line to user.js: user_pref("middlemouse.contentLoadURL", false);
Then start Firefox again - it works!