Thanks to Ed Street, SCHWACK and Ray Olszewski.
to Ed Street, I am not using dhcp, but i assign ip manually
to SCHWACK, I have try using (http_access deny person), but that's not work.
to Ray Olszewski, what i mean is browsing the web whole day and downloading big data from ftp server
My proxy using the port to access web. if i change the port (using http_port), all client in my network can't access the web
and this is not i want. I also realize when i change the port, some of the client still can using icq or other and they still can using outlook express