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.
A firewall controls what programs can access the Internet. Find information about configuring your firewall to allow Firefox access to the Internet.
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.
After the update to Firefox 63, some users with Quick Heal security software might be impacted by tabs repeatedly crashing. This article explains how to fix that.
This article describes how to troubleshoot problems, like those with games or chat, that you might encounter while using Facebook in Firefox.
This article explains how to fix problems where a website doesn't look like it normally does or does not load correctly.
If no web browsers on your computer can load websites, it indicates a problem with your Internet connection. The article describes some troubleshooting methods.
Learn to troubleshoot and fix problems connecting to websites that start immediately after updating to a new version of Firefox.
How to resolve login issues if your bank still uses a non-standard digital certificate (SignText) that Firefox no longer supports.
Learn why you might see time-related errors on HTTPS websites and how you can troubleshoot these errors by correcting your system clock.
If you find that you can't log in to a website that requires a username and password, follow the steps described in this article.
Are you having trouble getting a website to load? This article will show you how to fix the problem so you can get back to surfing the web.
Sometimes a website will start to load, but never finish. This article covers possible solutions.
Find out the right direction to get help using webmail in Firefox and links to support pages for popular web-based email services.