What's your computer system and Firefox version?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Thanks - I tried that - did not work Computer MACBook Pro OSX 10.12.1 with no antivirus Firefox - 50.0.1 here is the entire quote I get from the error screen

"The owner of search.yahoo.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate."

https://support.mozilla.org/en-US/kb/update-firefox-latest-version 50.0.2

There could be a probleem with the site itself.

Have you tried; https://www.yahoo.com/

Hi robsj, can you find an "Advanced" button on that error page? If so, please click that to find more technical details about the error. Often you'll see a blue code that matches this article:

How to troubleshoot security error codes on secure websites

But there are several other possible error codes so it's best if you can find one and let us know what you're getting.

In some cases, clicking the code will open a further panel with an encoded version of the certificate that Firefox is objecting to. You can copy/paste that into a reply for analysis. What I do with that is paste it into one of these sites to inspect the certificate details to see whether that flags up the problem:

• https://www.sslchecker.com/certdecoder
• https://certlogik.com/decoder/

If you end up doing the decoding yourself, could you report back on anything you learn?

I pressed the wrong button!! This did not provide the solution to the problem This ONLY occurs with 'all' of the search engines - it appears that all other sites are ok.

here is what came up on the advanced button. I checked on the decoder site, but i confess it meant nothing to me. Here is the text

search.yahoo.com 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

this is the certificate text

https://search.yahoo.com/yhs/search?p=trains&ei=UTF-8&hspart=mozilla&hsimp=yhs-003 Peer’s Certificate issuer is not recognized. HTTP Strict Transport Security: true HTTP Public Key Pinning: false Certificate chain: -----BEGIN CERTIFICATE----- MIIGQTCCBSmgAwIBAgIRAP7TdwSC20Va8IEP/0JeFbswDQYJKoZIhvcNAQELBQAw KzELMAkGA1UEBhMCRU4xHDAaBgNVBAMME0FkZ3VhcmQgUGVyc29uYWwgQ0EwHhcN MTUwNDIzMDAwMDAwWhcNMTcwNDIyMjM1OTU5WjCBhzELMAkGA1UEBhMCVVMxEzAR BgNVBAgMCkNhbGlmb3JuaWExEjAQBgNVBAcMCVN1bm55dmFsZTETMBEGA1UECgwK WWFob28gSW5jLjEfMB0GA1UECwwWSW5mb3JtYXRpb24gVGVjaG5vbG9neTEZMBcG A1UEAwwQc2VhcmNoLnlhaG9vLmNvbTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCC AQoCggEBAKQw2uWsQmcdERncsSJjUAKL7oDEzDtcFW2lLHXOM+35X7LRDOMGtwAW yj/Ev2+coFvU4tBBPr+b6KxWMNTCmtBGCUa53ENVq3RB99QLmgxsRkLhXSwAOKgF jSroG4qIxr6QMR6qQ1oxE28TuGCiL8SrCVx/DOeKOzYUXOeZnlpGSOW9oQZAslkx ujuZmYjZ0d8Frbnhbh3AqwHzrKBndL+4oHMTiz/F42Zsm8thrW7ampQs0I4vfG7a lYqjdkAD2Y/6SHcNtJGH9hpH5Ujjzd5jMKCkep8svA50XQHkEwTUQ/MxPSOYrUJN GWhFIz5halWjzyjh07hSTHvfkrI7zUcCAwEAAaOCAwEwggL9MIICzwYDVR0RBIIC xjCCAsKCGiouYW5zd2Vycy5zZWFyY2gueWFob28uY29tghgqLmF1dG9zLnNlYXJj aC55YWhvby5jb22CFyouYmxvZy5zZWFyY2gueWFob28uY29tghwqLmNlbGVicml0 eS5zZWFyY2gueWFob28uY29tgh0qLmRpY3Rpb25hcnkuc2VhcmNoLnlhaG9vLmNv bYIaKi5maW5hbmNlLnNlYXJjaC55YWhvby5jb22CGCouZm9ydW0uc2VhcmNoLnlh aG9vLmNvbYIYKi5nYW1lcy5zZWFyY2gueWFob28uY29tghkqLmltYWdlcy5zZWFy Y2gueWFob28uY29tghwqLmtub3dsZWRnZS5zZWFyY2gueWFob28uY29tghwqLmxp ZmVzdHlsZS5zZWFyY2gueWFob28uY29tghgqLmxvY2FsLnNlYXJjaC55YWhvby5j b22CESoubG9jYWwueWFob28uY29tghAqLm1hcHMueWFob28uY29tghkqLm1vdmll cy5zZWFyY2gueWFob28uY29tghcqLm5ld3Muc2VhcmNoLnlhaG9vLmNvbYIaKi5y ZWNpcGVzLnNlYXJjaC55YWhvby5jb22CEiouc2VhcmNoLnlhaG9vLmNvbYISKi5z ZWFyY2gueWFob28ubmV0ghgqLnNoaW5lLnNlYXJjaC55YWhvby5jb22CGyouc2hv cHBpbmcuc2VhcmNoLnlhaG9vLmNvbYIZKi5zcG9ydHMuc2VhcmNoLnlhaG9vLmNv bYIVKi50di5zZWFyY2gueWFob28uY29tghgqLnZpZGVvLnNlYXJjaC55YWhvby5j b22CDmJvc3MueWFob28uY29tgg9sb2NhbC55YWhvby5jb22CDm1hcHMueWFob28u Y29tghBzZWFyY2gueWFob28uY29tghBzZWFyY2gueWFob28ubmV0MAkGA1UdEwQC MAAwHQYDVR0lBBYwFAYIKwYBBQUHAwEGCCsGAQUFBwMCMA0GCSqGSIb3DQEBCwUA A4IBAQB1hreRRbN1p7bGKcIhhZ93ItOp+SQMUY+kfdOnc3FOnSwheKJ/YqacFAF7 9C0OqGKtRM/BG/vzX7hdyimehXfaLaeK+P4PpKeslIuylhLiUctnyKU+0Imid7Eg 4TbkzwGgSqP+FKL8fNUOy+RiaJpmSvt6/4SaAaxOKfp9l50HKMEM+qTGzrwTHGDU R5RWnDUrHKRDXDqtmO+nfJB5XSFsrJSShggt+reWstG45Bgb1DSGd3thIrOVh7iV uqEl0Dn9ddNC1pPnI7npoj9V7YNCV3TxQDD36plm3fduI3zN9TSG98HD2BDMSngj LM8pfTbWH/ZBAMr4V0F6qMr+P2Qh -----END CERTIFICATE-----

Hi robsj, the certificate issuer is listed as "Adguard Personal CA". So I assume you use Adguard. Try:

https://kb.adguard.com/index.php?/Knowledgebase/Article/View/21/0/the-connection-is-not-trusted

Any luck?

thanks to everyone who took the time to help me - it is greatly appreciated! I was indeed using adguard and forgot that it was active.