*Ip does it need DNS to find a machine on the internet?

If I have an IP address but no domain name connected to it, would I be able
to connect to my www server by using the IP. I'm on a sat internet system
and just wanted to try out the iis on xp pro. I can get my computer if I use
the IP from the same machine. But If someone from the WEB types in the IP it
doesn't work. It maybe because my isp is blocking port 80. Also I understand
most of the things about DNS, how it uses name servers to locate the IP
address, "But" How does WEB know where all these addresses are in the real
world! What subject heading would that be under so I could do some reading.
It seems to me that DNS is play time compared to What gos on when it comes
to locating the computer that has the address xxx.xxx.xxx.xxx, If someone
out there know anything about this part of the WEB I would be very thankful
if you could pass it on to me.
Thank you every one, this is a very well informed News Group.