Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Are you unable to access HTTP addresses, or is the problem limited to HTTPS addresses?

Examples:

http://www.jeffersonscher.com/

vs

https://www.jeffersonscher.com/

The login state is stored in a cookie, so make sure that you do not block cookies.

• http://kb.mozillazine.org/Cookies
• https://support.mozilla.org/kb/Cookies

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• Do NOT click the "Refresh Firefox" button on the Safe Mode start window

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

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

• Firefox/Options/Preferences -> Advanced -> Network -> Cached Web Content: "Clear Now"

"Remove the cookies" from websites that cause problems.

• Firefox/Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: "Show Cookies"

And if all of that did not help

Testing Firefox, Backup your firefox

You got problems with an updated version of firefox and want to test if it is because of the update.

Ok here is an easy way to test. Simply get yourself the version you used before updating "as Portable". Firefox portable Download page

After download your fox portable is here: C:\Users\Your Account Name\Downloads\FirefoxPortable64-47.0.1

Now on your Win10 go to your installed account profile here, Win 10; C:\Users\Your Account Name\AppData\Roaming\Mozilla\Firefox\Profiles\o65hyi78.default [You have different number]

The folder that has .default behind it is your saved logins and bookmarks. Right click copy that folder

Here is your portable profile folder, do paste inside it, to copy your profile to it: C:\Users\Your Account Name\Downloads\FirefoxPortable64-47.0.1\FirefoxPortable64\App\DefaultData\profile

Inside the root folder are 2 firefox links, but go to this one the portable does not have your profile: C:\Users\Your Account Name\Downloads\FirefoxPortable64-47.0.1\FirefoxPortable64\App\Firefox\firefox

Now you and created a backup of your bookmarks and saved passwords, And you can test if fox works on the old version. And you can use the portablefirefox in the main root folder to start without your profile in it, so then you can test ;)