Please ensure that the date, time and timezone on your system is configured correctly. Sometimes an improper time setting can cause your computer to block websites because the security certificate becomes invalid.

If your date and time and timezone are all configured correctly, there may be malware on your computer that is attempting to redirect you to an insecure website. Further information can be found in the Troubleshoot Firefox issues caused by malware article.

My date and time on both computers are correct. I've disabled AVG on my windows 7 machine and my windows 8 has no malware. accounts.firefox.com is the only site i'm having issues with.

Please note that AVG does not detect all malware, so it is possible that you may still have an infection on your computer. Scanning with the tools provided in the article I originally shared with you will ensure that you have no infection.

Generally, when the issue occurs on other internet browsers, it means that it is not a Firefox related issue.

Please ensure that you are not using a proxy server to access the internet.

Here are some screenshots of my issue

You can also refer to these articles:

• "This Connection is Untrusted" error message appears - What to do
• Secure connection failed and Firefox did not connect

You can also rename the cert8.db file in the Firefox profile folder to cert8.db.old or delete the cert8.db file to remove intermediate certificates that Firefox has stored.

If that helped to solve the problem then you can remove the renamed cert8.db.old file. Otherwise you can rename (or copy) the cert8.db.old file to cert8.db to restore the previous intermediate certificates. Firefox will automatically store intermediate certificates when you visit websites that send such a certificate.

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder