Problem with CGI Java chat

Hi,
I am getting this error message:
The server encountered an internal error or misconfiguration and was
unable to complete your request. 
Please contact the server administrator, [email protected] and inform them
of the time the error occurred, and anything you might have done that
may have caused the error. 

More information about this error may be available in the server error
log.
 
The URL I tried was:
http://www.blitzed.org/java/chat.phtml
 
Regards,
   John