Internet Facing Site on Port 80

Is it proper to build an internet facing site on port 80? If yes is there need for Alternate Access Mapping?

I created a web application on port 80 for an internet facing site using sahrepoint 2010 running on windows server 2008 and sql server 2008. I went on to do the access mapping as follows:

Zone: Default;

Internal URL: http://myservername;

Internet URL: http://www.mycompany.org

Now the problem is that this is not working. Should I move to a new port number?