This should be a very easy one.. hopefully

I tried to set up my computer as server (Win98 + Apache), but it doesn't work. I can type in 127.0.0.1 or my internal network IP which shows me the home page, but when I try my real IP it doesn't work.
I thought it's because I have the wrong IP (winipcfg shows me just the internal IP from my provider's network (They use a Squid proxy)), but I tried to ping the IP and that works...

Has anyone an idea why this could be?

Thanks in advance