@ Sandy: The main purpose of this is to provide a "close TAB" button. It should be renamed. It can be set to be a general close button, but firefox already has a close button like any windowed program so that is a feature few will find a use for. And if your Firefox doesn't have a close button that isn't Mozilla's fault, that's something wrong with your window manager. This does work for me - sometime - but not consistently. Trying to come up with a workable combination of addons and settings to salvage a usable UI out of the mess Mozilla made with Australis, I' ve been trying different things and sometimes this worked well, sometimes poorly, and sometimes not at all. At one point it was there in the customise window but there was no text only a lot of tiny pictures that were almost indistinguishable. I finally figured out which was Close Button and I tried to drag it to the toolbar and it dissapeared. Another time (I've unistalled and reinstalled it several times, because I NEED for this to work) I got it onto the toolbar but the icon and the sweet spot to click on were impossibly tiny. At one point a change of theme seemed to solve both problems - text showed up in the customise window and the button on the tool bar became TOTALLY invisible BUT the sweet spot spread out to cover all the remaining space on the menu bar (which I restored using Classic Theme Restore) making it plenty easy to click. But I've had to completely purge and reinstall FF since then, since it completely quit working, and now I can't drag and drop from the customise window and I can't put anything on the menu bar. Seems like before I can figure out how to configure FF they change it again. Now my problem is that Close Button doesn't show up in the customise window after I install it. So I can't get it on the toolbar. But when I had it there earlier, it did work, so I will keep trying. I don't blame the dev for this. I blame Mozilla. It's pretty hard to write software for a platform that's a rapidly and erraticly moving target. It's a wonder these guys keep trying. I think I'd have thrown in the towel. But the bottom line for me as a user is that even though Australis sucks and Mozilla devs seem to have caught the "dumb it down, pop it up, more glitter, less function" attitude (maybe they caught it from the Gnome group) FF unfortunately is, in practice, the only game in town if you want a browser with a lot of opportunity for customization. Unless you want to do a lot of coding yourself. I wish this extension had a forum. Anyway, when it works it's great. Maybe Firefox will stabilize a bit and give the extension devs a chance to catch up.