Firefox shows you a warning page about a potential security risk when you try to connect to a secure site but your connection is not secure.
Your organization or Internet Service Provider may offer or require you to use a proxy to connect to the Internet. Learn more.
Learn about the error codes SEC_ERROR_UNKNOWN_ISSUER MOZILLA_PKIX_ERROR_MITM_DETECTED and ERROR_SELF_SIGNED_CERT on HTTPS websites and how to troubleshoot.
If you can't connect to a website, you may see the Server Not Found error message. Learn how to troubleshoot and fix this error.
We'll explain errors such as "Server not found" or "Unable to connect" and how to fix problems where Firefox can't access websites but other browsers can.
A "Server not found" error can be caused by Windows Firewall blocking Firefox from accessing the Internet. Learn how to configure it to allow Firefox access.
Learn why you might see time-related errors on HTTPS websites and how you can troubleshoot these errors by correcting your system clock.