The requested URL could not be retrieved

While trying to retrieve the URL: http://www.google.es/

The following error was encountered:

    Unable to determine IP address from host name for www.google.es 

The dnsserver returned:

    DNS Domain 'www.google.es' is invalid: Non recoverable errors. 

This means that:

 The cache was not able to resolve the hostname presented in the URL. 
 Check if the address is correct.