I recently upgraded to Firefox 7. Occasionally I use middle-click a the History menu item to open it in a new tab, but it opened in the current tab instead. Unfortunately I don't remember which version I last tried it on. After running FF 7 for a while, I ran FF 6.0.2 again, and it also lacked the behavior. Either it never worked in FF6, or FF7 installed a new setting that affected FF6.
Does anyone remember the middle-click to open history menu item in new tab? Same goes for middle click to open bookmark menu item in new tab - doesn't work anymore.
Note that the lost feature only applies to click on menu items; new tabs do open if I actually use the separate history/bookmarks window ("show all history" or "show all bookmarks").
I'm on Mac OS X Leopard.
UPDATE: This bug report says that it hasn't been working since FF 3.6 . I guess it's possible I haven't used the feature since then...