I'm using K-Meleon an older laptop, and sometimes I'd like to close a tab without having to make it active first. That way I wouldn't have to wait for the page to load from cache again, which can take quite a while.
Unfortunately, when I right-click an inactive tab and hit the close command, it closes the active tab instead. I know I can undo that command, but it will take even longer, which bothers me every time.
I really didn't know about the middle click, this really changes a lot. Like I said, I use a laptop, but it can emulate a middle click by clicking both buttons at the same time. I think that's a standard feature nowadays.