There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

Did you try to clear the cookies for the Orange website ?

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows an highlighted shield icon at the left end of the location/address bar in case Tracking Protection is blocking content.

• click the shield icon for more details and possibly disable the protection

You can check in the Web Console what content is blocked.

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

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You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.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 for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" for websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Data"

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

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 -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website then data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

Responsable du problème : module complémentaire uBlock Origin. Qui va corriger ? Merci à tous. André

André VAYSSE said

Responsible for the problem: uBlock Origin add-on. Who will correct? Thank you all. André

Open that website. Then open the options for uBlock and disable it for that website.

Can I reply in two languages ? French and English.

I had the same problem with my orange.fr mailbox these past days, only when using Firefox with µbblock origin and AVG Online Security extensions. No problem using Chrome or Opera or Chromium bowsers which have the same extensions. After reading the different answers I went into µblock origin settings to have a look ; I changed nothing and instantly I could access to orange.fr ; might be something which clears itself in the white list. Thanks to Mozilla team to help us to clear this problem as it happens only with Firefox

J'ai eu le même problème ces jours-ci : je ne pouvais plus accéder à ma boite mail chez orange.fr avec Firefox avec les extensions µblock origin et AVG Online Security. Aucun problème d'accès avec Chrome, Opéra ou Chromium qui utilisent les mêmes extensions. Après avoir lu les différentes réponses, je suis allé dans les paramètres de µblock origin, j'ai regardé partout mais je n'ai rien changé et instantanément j'ai pu accéder de nouveau à mes mails orange.fr ; quelque chose a dû se débloquer automatiquement dans la liste blanche. Merci à l'équipe Mozilla de nous aider à gérer µblock origin puisque cela ne se produit qu'avec Firefox.