Firefox: This address uses a network port which is normally used for purposes other than Web browsing.

When browsing to some sites using Firefox, I got the message:

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

When you see this message, Firefox completely blocks you from accessing the site you have requested. Since people often need to access non-standard ports for development purposes, this is stupid - the kind of 'nanny' behaviour you would expect from Microsoft, not a company who are normally very 'developer friendly'.

There is of course, a way around it:

1. Open Firefox
2. Type about:config in the address field
3. Right click anywhere on the screen
4. Click new > string
5. Enter preference name as: network.security.ports.banned.override
6. Enter string value as: 2049 (or whatever port number you want)

When you attempt to visit the site again, Firefox will allow it since you have added an exception for the selected port.