This address is restricted
This address uses a network port which is normally used for purposes other than Web browsing. Firefox has canceled the request for your protection.
1. Open your Firefox.
2. Type about:config in your address bar and search for "network.security.ports.banned.override".
3. If "network.security.ports.banned.override" doesn't exist then right click anywhere in the windows and select New -> String and use "network.security.ports.banned.override" as preference name and then hit the "OK" button.
4. Enter the port number to the value box.
If you need to visit http://mail.yourdomain.com:1 and get this error message, then the blocking port is 1, so you add 1 to the box and click "OK" button. You can also select a range of ports by using "1-1024" as such a value or as a CSV style values such as "1024, 8080, 1-1000, 80"… etc
5. Once everything is done, you can try again to visit the same URL.