Certificate warnings

Firefox uses certificates on secure websites to ensure that your information is being sent to the intended recipient and can’t be read by eavesdroppers.

Certificate will not be valid until (date)

This error can occur if your computer clock has the wrong date, in which case the date given in the error message will be in the past. To fix the problem, set your system clock to today’s date and time.

The certificate expired on (date)

This error occurs when a website’s identity certification has expired.

This error can also occur if your computer clock has the wrong date. To fix the problem, set your system clock to today’s date and time.

The certificate is not trusted because the issuer certificate is unknown

The file cert8.db in your profile folder may have become corrupted. Delete this file while Firefox is closed.

1. Open your profile folder:Click the menu button , click help and select Troubleshooting Information. The Troubleshooting Information tab will open.
2. Under the Application Basics section, click on Open Directory. A window with your profile files will open.

1. Click the menu button and then click Exit .

2. Click on the file named cert8.db.
3. Press Delete.
4. Restart Firefox.
   cert8.db will be recreated when you restart Firefox. This is normal.

The certificate is not trusted because no issuer chain was provided

You may have enabled SSL scanning in your security software such as ESET or BitDefender. Try to disable this option.

The certificate is not trusted because it is self signed

or

Self-signed certificates make your data safe from eavesdroppers, but say nothing about who the recipient of the data is. This is common for intranet websites that aren’t available publicly.

The certificate contains the same serial number as another certificate

This error alerts you to the fact that the certificate the page you’re visiting uses has a serial number identical to one you’ve already accepted. This warning cannot be bypassed using the method below.

Bypassing the warningYou can tell Firefox to bypass these certificate warnings. You should only bypass the warning if you’re sure that the site is legitimate. Legitimate public sites will not ask you to do this. An invalid certificate can be an indication of a web page that will defraud you or steal your identity.

1. On the warning page, click Or you can add an exception….
2. Click Add Exception…. The Add Security Exception dialog will appear.
3. Click Get Certificate.
4. Read the text describing the problems with this site.
5. Click Confirm Security Exception if you want to trust the site

By: Mozilla Support