A Java Based MSN client. With Mercury you can do the same things as with your normal messenger. But Mercury has some extra functions that your normal messenger doesn't have, for example: Be online with several MSN adresses at the same time. Login with your status on 'Invisible' or any other status you want. Have a different MSN name in every conversation. Use and create your own plugins. See when someone starts a conversation with you (before he says something). See when someone closes the chat conversation window. See who added you into a conversation with multiple people. See when someone deletes you from their contactlist. See the difference between MSN, Mercury users and webcam capable MSN users. Many more features.