[squid-users] standard Error messages

where do I find the standard Error messages which posted to the Clients
ERROR
The requested URL could not be retrieved

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While trying to retrieve the URL: http://www.ebay.de/
The following error was encountered:
  a.. Access Denied.
  Access control configuration prevents your request from being allowed at
this time. Please contact your service provider if you feel this is
incorrect.
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Generated Wed, 03 Apr 2002 14:01:45 GMT by www-cache.dw-westfalen.de
(Squid/2.2.STABLE5)
mit freundlichen Gruessen
Juergen Lucka
(EDV-Koordination)