[squid-users] help:url not retrieved

[mauro]

Hello.
After configuring a browser to connect to squid at localhost, I receive an 
error page of url not retrieved because forwarding denied. It specify that 
the cache will not forward the request because it is trying to enforce a 
sibling relationship.
Have you some hints to resolve it? Could you suggest me the part of 
configuration guide where I have to detect?
Thanks in advance