OK, the first main thing you need to remember is that there are two kinds of IP addresses: Internal (within a company/home/organization), and external (out on the Internet). If your friends are outside of your company/home/organization (i.e., they're external), then an IP address that you use internally will not work for them UNLESS it's a valid external IP address.
For example, the machine I'm sitting at right now has an INTERNAL address of 192.168.1.101. That IP address is ONLY internal, however; it doesn't work for anyone else except me, and only within my organization. Other people may also have 192.168.1.101, but that address refers to a machine inside THEIR organization, not mine. My external address, for the sake of argument, is 17.100.200.1*; only if that address is reachable from the Internet (i.e., it's external) can someone use it to reach your machine. If I had my router configured to route incoming port 80 traffic (Web site traffic) to a machine inside my organization, then you could access my web site via 17.100.200.1.
So, the question is, where are your friends? If they're outside your organization, you will need to set up your web server and router so that the server is visible to the Internet. If you can't do this, you're out of luck.
DNS servers, BTW, are machines that translate Internet names (e.g.,
www.apple.com) into IP addresses (e.g., 17.1.1.1) so that programs know where to go.
Oh, and 10.x.y.z is NOT a valid Internet address, if I remember correctly. That's reserved for internal addresses ONLY. That may be why your friends can't access it.
* Not a real address, as far as I know.
