If the FTP server requires an account name and password or is using a different port number than the default, then one cannot just write the address for the FTP.
It is possible to give login/passwd and port number in the url:
The login and the passwd is separated with a " : ".
There is a " @ " to separate the address from the login and passwd.
The port-number is separated from the address with a " : ".
If only the address is specified, then the Internet Explorer will login as anonymous with no password and connect to port 21.
Note with Internet Explorer 7 the ability to perform ftp upload has been removed, and one instead have to browse the FTP using Windows Explorer.
Related Enable passive FTP mode in Internet Explorer