That's an FTP URL not an HTP (HTTP) one.
It should work in the path field if the phone allows anonymous access. Alternatively, try it in FTP > Quick Connect, which also lets you type in a username and password.
You would not normally map a drive to an FTP server. That's usually for network shares (sometimes called SMB shares) which are a different thing.
The FTP FAQ has more suggestions if that doesn't work.