router allows port forwarding, but access still isn't available

Okay, I just bought a router, it allows port forwarding. I'm trying to set up a website (just for fun). I allowed port forwarding to my computer. But when I type my internet IP into the address bar, my modem (it looks like my modem configuration interface) says:
User Login - Failed

Access permission is currently denied

I made sure to forward port 80. My router is netgear websafe router rp114.

 

Your isp is more then likely blocking incoming port 80 as generaly they dont allow home users to run webservers off there connection. Try a different port.

 

I've never setup anything like this on a home network, so I'll ask a question of ignorance: If you're testing the website from a computer on the internal network (perhaps even the same computer that's hosting the site), do home routers ever encounter problems with double NAT'ing? Let's say my ISP assigned IP address on the external interface of the router is 123.456.789.123 (intentionally bogus) and I have a statically assigned IP address on the web server of 192.168.1.5. Let's also assume I'm testing from the same computer. My router sees traffic from 192.168.1.5 from source port [insert high port number here] and is destined for port 80 on 123.456.789.123. The router then NATs that back to 192.168.1.5 with a destination port of 80. When the web traffic returns, are home routers smart enough to translate the traffic back through 123.456.789.123 to the same 192.168.1.5 internal address? I guess sniffing the traffic and watching what goes out and comes back would tell you. In the scenario described, even if the ISP is dropping inbound traffic on port 80, the traffic may not ever be hitting their network. Are you able to access the web server using a computer outside your home network?

 

One other thought: If the router can be externally managed, it may already be listening on port 80 and there might be a conflict when you try to forward that port. :confused