Many ISPs block port 80 (HTTP) and port 25 (SMTP), as well as some other ports to home users. Typically, their response to this is that these protocols are "business related" or something along those lines. I assume this is the case for you.
Port 80 is the standard for HTTP. When you typer
superuser.com into your browser's address bar, it assuming two things:
- Since you left the protocol out, it assumes HTTP (http://superuser.com)
- Since you left the port out, it assumes port 80, based on the HTTP assumption (http://superuser.com:80)
Since port 80 is not an option, you need to find an alternative port. There is no official HTTP alternative port.
When port 80 is used for one address/webserver, it's fairly common to use port 8080 or 8000 for another site on the same address/webserver. This is most likely because they are similar enough to 80 that they are easy to remember. I have seen this done for external facing sites as well.
Alternatively, you can use any port you want. See this list of standard and unofficial ports. You could run it on port 23, if you didn't plan on using telnet to your Linux machine. In a web browser, you would just type