Wild_Eep: Well I've never seen that before, but I rarely use Firefox these days (its new Australia format runs like a slug on my rig. I find the new preferences etc. confusing / hard to navigate, and it took me a while before I could get the menubar back - without which you can't do much!)
I'm not a big fan of Australis either, but Firefox is the best of a bunch of bad options for me, so I found a solution.
Classic Theme Restorer That extension lets you set up your Firefox UI however you want. In fact, it was featured by Mozilla as one of two shining examples of how Australis is much easier for extension developers to modify without breaking something. (The other example being an extension which is to Chrome's minimal UI as Chrome's minimal UI was to the old Netscape Navigator-style UI that Firefox and Internet Explorer both used to have.
Of course, I still agree with
Jeff Atwood's view that Mozilla is using their extension ecosystem as an excuse to abdicate their responsibility to provide a reasonable set of defaults and customization options out of the box.
(If your browser requires a dozen extensions just to get simple, obvious things that are standard elsewhere, like scroll-wheel tab switching and menus that are consistent with the look and feel of the host platform, then
yes I
will blame you for any bugs or performance problems caused by those extensions.)