A user name if authentication is to be used.
This property contains a user name if authentication is to be used. If AuthScheme is set to HTTP Basic Authentication, The User and Password are Base64 encoded and the result is put in the Authorization property in the form "Basic [encoded-user-password]".
If AuthScheme is set to NTLM, NTLM authentication will be attempted. If AuthScheme is set to NTLM and User and Password are empty, the class will attempt to authenticate using the current user's credentials.