I'm gathering the website is on your server, and not your ISPs server?
Check your httpd.conf file, and make sure the line:
"AddHandler cgi-script .cgi"
...is not commented out.
This tells Apache how to handle CGI scripts. By default, it may be disabled.
If it is commented out, uncomment it, and restart your apache server. See if that helps.
On a side note, CGI scripts operate through port 80 just like any other HTML data sent down to you, unless explicitly told not to in the program (Eg: Some client-server app).