It means that the DNS service is not working properly on either your side or the server's side. Changing DNS server to Google DNS or OpenDNS , or remove all cookies and cached files on your browser will help to resolve this issue immediately. Like any other error, there are several ways you can solve problems by yourself.
Release or Renew Your IP Address
Change DNS server
Restart DNS Client service
Reset hosts file
Reset Chrome Flags
Reset Winsock program