You must be joking

that's a configurable option. I don't remember when I first ran into it, but I hunted down how to disable it and have happily used the middle mouse button to open a link in a new tab instead (I got _so_ annoyed at slightly missing a link or text bar and the entire page disappearing on my when firefos opened some random URL that it thought I wanted to go to, or a search for the text that happened to be in the clipboard)