Mozilla Firefox Help

On websites which are supposed to be secure (the URL begins with "http s ://"), Firefox must verify that the certificate presented by the website is valid. If the certificate cannot be validated, Firefox will stop the connection to the website and show a "Warning: Potential Security Risk Ahead" error page instead. Clicking the   button, you can view the specific error Firefox encountered. This article explains why you might see the error codes SEC_ERROR_UNKNOWN_ISSUER, MOZILLA_PKIX_ERROR_MITM_DETECTED or ERROR_SELF_SIGNED_CERT on an error page and how to troubleshoot it.  Fix Firefox Error What does this error code mean? During a secure connection, a website must provide a certificate issued by a trusted certificate authority to ensure that the user is connected to the intended target and the connection is encrypted. If you click the button on a "Warning: Potential Security Risk Ahead" error page and you see the error code SEC_ERROR_UNKNOWN_ISSUER or MOZIL...

All of your personal settings, bookmarks, and other information are kept in your  Firefox profile . Firefox needs an unlocked profile to start up, and if the profile is locked, it displays the message,  Firefox is already running, but is not responding . This article explains what to do if you see this message and how to prevent it from showing at startup. End Firefox processes If Firefox did not shut down normally when you last used it, Firefox might still be running in the background, even though it is not visible.  If you try to open it while it's running, an error message will appear with the option to click  Close Firefox . If that doesn't solve the problem, restart your computer or try the following options.  Fix Firefox Error Use the Windows Task Manager to close the existing Firefox process Right-click on an empty spot in the Windows task bar and select  Task Manager  (or press  Ctrl + Shift + Esc ). When the Windows Task Manager opens, se...