cachesputnik.ru uses an invalid security certificate. The certificate is only valid for the following names: *.sputnik.ru , sputnik.ru (Error code: ssl_error_bad_cert_domain) If you understand what's going on, you can tell Pale Moon to start trusting this site's identification. Even if you trust the site, this error could mean that someone is tampering with your connection. Don't add an exception unless you know there's a good reason why this site doesn't use trusted identification.