The requested URL could not be retrieved

While trying to retrieve the URL: http://userfiles/File/aaparastari/darbare%20daftar%20parastari/amalkard90-%20sabzevar.pdf

The following error was encountered:

Unable to determine IP address from host name for userfiles

The dnsserver returned:

Name Error: The domain name does not exist.

This means that:

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

Your cache administrator is

Generated Wed, 19 Sep 2012 08:11:44 GMT by CacheServer (squid/2.6.STABLE4)