One special case is /http:/, if you set this location, a link formed like this: <a href="/http:/localwww/foo">mywwwserver</a> will enable accesses to local WWW-servers through a firewall.
Example:
# All hosts inside *.rydnet.lysator.liu.se has to be # accessed through lysator.liu.se .*\.rydnet\.lysator\.liu\.se 130.236.253.11 80