I am only a basic computer user, but I have downloaded Firefox and I cannot do any searches. I know there is a problem just with google as I get this message: www.google.co.uk 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 Even a basic search gives this error. If i change search engines to yahoo for example, it works fine. I cannot believe that google is causing this security problem. Upon further investigation i do get this message also: https://www.google.co.uk/search?q=fred Peer's Certificate issuer is not recognised. HTTP Strict Transport Security: false HTTP Public Key Pinning: true Certificate chain: I have changed my search engine from google.com to google.co.uk and still get the same error Can someone please help me :(