cannot find open link

I have problem with our website, my OS is Windows NT server 4.0 proxyserver 2.0, IIS 4.0 and MS Exchange Instaled in one server. My Problem is when I open our website from outside network I cannot open it, I search the Microsoft Knowledge Base andI found Knowledge Base Article 258546 I apply it, and I can now retrieve my website but I cannot open the link that is not located on my server or located on other computer in our LAN. I can access the link on our LAN but I cannot open it on outsidenetwork? What is the problem with the webserver and how can I fix this?