Today I ran into this warning from iceweasel when I tried to access a web service on port 101:

This address is restricted

This address uses a network port which is normally used for purposes other than Web browsing. Iceweasel has canceled the request for your protection.

I found this article which said:

• Open about:config
• Create network.security.ports.banned.override if it’s not there
• Set that setting as, e.g.: 101-104
• Refresh the page