You may be in Full Screen Mode. Tap the F11 key once to see if your toolbars reappear. The F11 key will toggle Full Screen Mode on and off with each tap.

• See - http://kb.mozillazine.org/Netbooks#Full_screen
• See - https://support.mozilla.org/en-US/kb/how-make-firefox-and-websites-go-full-screen

Be sure that the Navigation Toolbar is checked so that it will be displayed (your Location/URL and Search bars are on the Navigation Toolbar by default, unless you moved/removed them).

• See - https://support.mozilla.org/en-US/kb/navigation-buttons-missing
• See - https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars

The top of your window may be off screen.

• See - https://social.technet.microsoft.com/Forums/en-US/w7itproui/thread/f3040564-0457-4c91-af71-dce1bc673a99/
• See - http://superuser.com/questions/53585/how-to-move-windows-that-open-up-offscreen
• See - http://www.interworks.com/blogs/jvalente/2009/12/30/finding-your-screen-window-or-application-windows-7

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

• http://kb.mozillazine.org/Error_loading_websites
• http://kb.mozillazine.org/Browser_will_not_start_up