Check that Firefox isn't set to run as Administrator.

You can open the Properties of the Firefox desktop shortcut via the right-click context menu and check the "Compatibility" tab.

Make sure all items are deselected in the "Compatibility" tab of the Properties window.

• Privilege Level: "Run this program as Administrator" should not be selected
• "Run this program in compatibility mode for:" should not be selected

Also check the Properties of the firefox.exe program in the Firefox program folder.

Thank you for your response. I did what you described to do (administrator off, run as ... off, all other fields off but it is still not working. Right now I can open firefox in a new window. But when I try to enter address (i,e, yahoo.com ) it gives me the following message: Unable to connect. An error occured during a connection to mail.yahoo.com The computer has internet access

Thanks

It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application. Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/en-US/kb/server-not-found-connection-problem
• https://support.mozilla.org/en-US/kb/Firewalls
• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

Thank you again very much. Richt now I am in "Firestone Installer Properties", sub-section "Security" At this time the permission is for "system" which allows full control, modify, read & execute, read, write. It doesn't allow nor deny for special permissions or advanced settings. However I can click "advanced" to change those special permissions. Do I need to do That maybe? Or maybe I have to change the permission for the "system"?

Thank you for your patience.