Web Access

I have configured a proxy server 2.0 on my network then I put the web server behind the proxy with a local address.
When I try to access the website internally by domain name I get the default web page for Windows NT 4.0 Option Pack displayed.
When I use the local IP address for the web server internally the page come up.
When I try to access the page from the Internet out of my network, I get a blank page.
Does anyone have any ideas of what I am doing wrong?
Thanks