How do I change the 'Access Denied' mesg?

When someone tries to access a blocked site, the message:

--
Error
Access Denied
Sorry, you are not currently allowed to request
             http://www.examplesite.com
From this cache. Please check with the cache administrator if you
believe this is incorrect.
Generated by squid@server.......
--
appears. I've tried reading the FAQ and all the archived posts, but I
can't find any information on how to change this message. Which file,
and where, do I need to modify to change this message to something more
informative? I'm running Squid ver 1.1.10 (will be upgrading in about a
month) on a FreeBSD system.
Thanks in advance.
Ben