If I set the Internal Port Start and Internal Port End to 8080 (rather than 80), nothing changes.
Attempting to access the page normally, http://216.123.238.123 , gets me to the login window for the router. Attempting to access it with the port number, http://216.123.238.123:8080, gets a "Firefox can't establish a connection to the server" screen.
In that the eventual users of the web server are going to be using conventional URLs, such as http://www.myserver.com , rather than http://www.myserver.com:8080 , this is going to need to work without the router wanting to respond to HTTP requests on the default port of 80 (by asking for a router login password.)
What can I try next?
::Jack