Rather than hunting down the X to close your current tab, what if all you had to do was wish upon a star, and then right click anywhere on the tab you wish to shut down? I will let you know how to get that done, without the need of the “wishing upon a star” part.
The add-on you want to grab to get this done is Rights To Close. This extension enables a user to close the current tab by simply right double-clicking, with your mouse, anywhere on the web page. This cleverly named add-on works very well, and gets the job done.
It is a tiny extension, but it is really handy to have. You can pick up Rights To Close on the Firefox Add-ons web site.