This will recreate the cert8.db or cert9.db file once again and now you should not have any security certificates related errors. In the Firefox profile folder, locate a file named cert8.db or cert9.db and delete it.When the Firefox profile folder opens up, close all the Firefox browser windows and wait for ten seconds to let the Firefox processes to be terminated.On the troubleshooting page in Firefox, scroll down and click on the Show Folder button to open your default Firefox profile folder.Then select Help → Troubleshooting Information from the menubar. Press the Alt key on your keyboard to make the menubar visible in Firefox.You can then fix the certificate database in this way: If correcting the system time does not fix the problem, then perhaps it is possible that the certificates store database in your Firefox profile has become corrupt. You can correct the date manually, or you can use our UpdateTime tool to automatically update the date and time from NTP servers. If the date and time is not correct in your PC, then Firefox will be verifying the certificates using a wrong date and will give errors. While there could be problem in the certificate configuration on the web server itself, these errors in Firefox could also result from some local Firefox certificate database corruptions.įirst thing you should check is the system date. But if there is some problem with the certificates downloaded from these websites or if they cannot be verified, then Firefox will refuse to connect to the websites trying to use such certificates. When you connect to websites over a secure connection (HTTPS), the connection is encrypted using a security certificate issued by one of the certificate issuing authorities like Comodo, GoDaddy, Verizon, Symantec, Digicert etc.

Firefox 3.6.28 invalid certificate