The best way to test is from the outside.
Some routers do not support bounceback, where internal servers hit the external (real world) IP address and get redirected back into the network.
Apple's original Base Station did not support this. I don't know if your Netgear does or not.
Secondly, even if testing from the outside, many broadband providers (especially cable companies) specifically prohibit port 80 traffic on residential accounts. This is designed to prevent abuse of the service (running servers is usually a violation of the Acceptable Use Policy (AUP)), and also helps deal with the myriad of compromised Windows servers that are leaking CodeRed and other worms/trojans that have caused havok on the internet in the past.