There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate.

http://www.ehow.com/how_11385212_troubleshoot-reset-connection-firefox.html

https://support.mozilla.org/en-US/kb/server-not-found-connection-problem

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

http://kb.mozillazine.org/Error_loading_websites

https://www.bing.com/search?q=web+site+access+denied

https://support.mozilla.org/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

This Connection is Untrusted is sometimes caused because the computer system clock is wrong. Check the time / date / time zone settings.

sorry but it has something to do with the network and nothing to do with

virus scanners firewalls ...

IE works Chrome works

it is very specific to Firefox and only Firefox !!!!!

hi, if you'd like to solve the issue and not just complain about it, we'd need some more information about the issue, because a solution depends on your individual circumstances:

• what is the error code shown when you click on advanced on that error page?
• please also give us more information about the error by clicking on the error code, copying the text to the clipboard and then pasting it here into a reply in the forum.

thank you!

".... and not just complain about it...." <--------------- unnecessary

going to this page (or any page anywhere)

https://www.mozilla.org/en-US/firefox/48.0.2/firstrun/

www.mozilla.org uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER

https://www.mozilla.org/en-US/firefox/48.0.2/firstrun/

Peer's Certificate issuer is not recognized.

HTTP Strict Transport Security: false HTTP Public Key Pinning: false

Certificate chain:

Does <DELETED> ring a bell? That's not the normal issuer of the mozilla.org SSL certificate. There may be a company proxy server functioning as a "man in the middle".

Typically administrators add the proxy server's signing certificate to the Windows certificate store, which covers IE, Edge, and Chrome. Firefox uses its own certificate store, so users either need IT assistance, or assuming it's a trusted intermediary, they can import the certificate themselves. As an example: https://support.mozilla.org/questions/1068675

Exported from chrome and imported into FF

everything works

Thank you