[nuttendorfer]

This has been this way for the last few versions or rather since they changed the UI in version 11 I think. This allows you do double click this array to return to window mode or "drag it down" from maximized which will return it to window mode (Windows).

[HelloMcFly]

What OS? I have Firefox for Windows and have no unclickable space between the top of the tabs and top of the screen. I've never experienced that before on any release I can remember.

[JungleGymSam]

See here: http://i.imgur.com/6LFXPbV.png

You don't have that tiny (2px?) gap?

[HelloMcFly]

I do have that gap visually, but I can click on it to focus on that tab.

[spyder]

It's clickable for me and focuses the tab when clicked.

[nuttendorfer]

Opera on Windows, sorry I should have made that clear.