How to troubleshoot security error codes on secure websites
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.
Troubleshoot Firefox issues caused by malware
Malware is software designed to invade a computer without your knowledge. We'll explain common symptoms, how to prevent it being installed and how to remove it.
Diagnose Firefox issues using Troubleshoot Mode
Use Firefox Troubleshoot Mode (known as Safe Mode in previous versions of Firefox) to diagnose and fix problems. Learn more.
Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems
Learn how to find out if an extension, theme or hardware acceleration is causing a Firefox problem and what steps you can take to fix it.
Troubleshoot and diagnose Firefox problems
This article includes a series of steps you can follow, that will help you fix most problems with Firefox.
Reset Firefox preferences to troubleshoot and fix problems
When troubleshooting Firefox problems, resetting user preferences can be helpful in pinpointing the issue. This article explains how to do it.
