Fixing Firefox Errors When Opening Secure Sites

Sometimes when you try to open a website over the secure connection using the HTTPS protocol (for example,, Mozilla Firefox gives up and shows warnings about invalid certificates, missing certificates, untrusted connection, mismatched domains and so on. All these errors are related to the SSL certificates of websites which are necessary to establish a secure encrypted connection between your computer and those websites. While you may encounter one or two websites, once in a while, that actually has missing, wrongly configured or expired SSL certificate, it is not usual to see these errors for large websites like Google or Yahoo!.

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If you are seeing these errors for sites from web giants like Google, Yahoo, AOL etc., then most probably the problem is on your end in Firefox configuration. You can follow these steps to repair Firefox certificates database and fix these errors:

  1. First of all check your computer’s clock and see if it is set to current date and time. If your system has dead CMOS battery, then it may show a date of many years ago causing problems in Firefox when accessing secure sites.
  2. Close all the open Firefox windows and use task manager to kill all the running Firefox instances.
  3. Press the Win+R key combination to open the Run dialog. Type %AppData% in the Run dialog and press Enter.Fix HTTPS Errors in Firefox
  4. Open Mozilla\Firefox\Profiles sub-folder inside the AppData folder that opens up. You will see a profile folder ending in the .default name – open this folder – this is your Firefox profile folder. For example, my profile folder is 2nqiz3vc.default – it is a random name assigned by Firefox and is different for everyone.
  5. Inside the Firefox profile folder, locate the file named cert8.db and delete it. There is no need of creating a backup of this file, as this file shall be rebuilt again by Firefox.Fix HTTPS Errors in Firefox
  6. Start Firefox and try to access a website through secure connection. You should be able to visit that site without any problems.

Conclusion: Sometimes Firefox throws up problems when you try to open websites over an encrypted secure connection through the HTTPS protocol. This could be due to file corruption in your Firefox profile and is very easy to fix.