Does anyone can tell me if it is possible to block all internet 
   access to certain users and allow just to some urls?
  
   Though, I didn't use it, 
    I know that in version 5.1.2 was a module in server manager, 
    That I could permit access to navigate to just some users 
    restricted to certains urls,  and I know that e-smith 5.6 is it 
    possible to block internet use using iptables, but how can 
    I just give access to certain users to certains urls, 
   Please let me know, 
   Thanks, 
    Ricardo