Geekspeak I don't understand

Can anyone tell me what this really means, and what might have gone 
wrong, or what's amiss in 'my setup'?

"An error occurred during a connection to www.facebook.com. The server 
uses key pinning (HPKP) but no trusted certificate chain could be 
constructed that matches the pinset. Key pinning violations cannot be 
overridden. (Error code: mozilla_pkix_error_key_pinning_failure)

     The page you are trying to view cannot be shown because the
     authenticity of the received data could not be verified.

     Please contact the website owners to inform them of this problem."
-- 
Roland Perry