Hello,

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be recovered unless they have been backed up to an external device!

Please report back to see if this helped you!

Thank you.

Firefox 29 and later versions have the Australis interface that looks different than the user interface in Firefox 28 and older versions.

• With the Australis interface the orange Firefox menu button has been replaced by the three bar Menu button at the far right end of the Navigation Toolbar
  A consequence of this new menu button is that you no longer can hide the Navigation Toolbar
• There is a star like button to the right end of the search bar on the Navigation Toolbar to bookmark the current web page and a "Show your bookmarks" button next to it to open the Bookmarks in a drop down menu
• It is still possible to have the menu bar visible via the right-click context menu on the toolbars to have menus like the the Bookmarks menu

See also:

• https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox

• https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox
• https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox

• https://support.mozilla.org/kb/what-happened-to-the-add-on-bar

• Tabs On Bottom: https://addons.mozilla.org/firefox/addon/tabs-on-bottom/
• The Addon Bar (restored): https://addons.mozilla.org/firefox/addon/the-addon-bar/

Sorry peter Jackson, I mismisunderstood the question, I initially thought you removed some file needed by Firefox to work.

Core-el has the solution, it's a change in Firefox australis.