Some APIs require basic authentification when calling. In the browser a login-window pops up and after inserting the correct username and passwort access is granted.
In such cases try “http://username:password@www….”.
See http://www.ietf.org/rfc/rfc1738.txt chapter “Common Internet Scheme Syntax”:
//<user>:<password>@<host>:<port>/<url-path>
