Are you running Firefox in full screen mode?

• https://support.mozilla.org/kb/how-to-use-full-screen

You can toggle full screen mode with the F11 key.

If you are in full screen mode then hover the mouse to the top of the screen to make the Navigation Toolbar and Tab bar appear.
Click the Maximize button (top right corner of the Navigation Toolbar) to leave full screen mode or right-click empty space on a toolbar and choose "Exit Full Screen Mode" or press the F11 key.

stevemcc said

The new one will not stay behind the taskbar no matter what I do, and I do not want the address bar or tabs disappearing. I have had it with trying figure the new version out. I just want an earlier copy.

I am not having the problem, my father is. He is running Vista and it doesn't matter whether he is in full screen mode or not. The taskbar will not appear as long as Firefox is running.

Is your father running Firefox in maximized mode?

If the Windows task bar set to be always on top via its properties?

He is not running in full screen mode, and the properties for the taskbar are set to always be on top. It doesn't matter. If Firefox is open it covers the taskbar.

If the Firefox window isn't maximized then at least you should be able to resize the Firefox window to make the Windows task bar visible.

The crazy thing is, even when it is not in full screen mode Firefox seems to want to use the bottom of the screen. I am having to try to solve this via TeamViewer since I am a thousand miles away from him. I came up with a work around for my dad tonight. I dragged his taskbar to the top of the screen and viola, Firefox does not block it if it is at the top of the screen.

Many of us are using Classic Theme Restorer (Customize Australis) {web link} Restore squared tabs, appmenu, add-ons bar, small button view and more on Australis UI (Windows/MacOSX/Linux + Fx 29+).

This will restore many of the things the last upgrades took away.