title: Retrieve User ID before application permissions
body: <p>Is it possible to retrieve an user id before agreeing to give permissions to an application?</p>
  
  <p>I'm trying to salute a user before agreeing to the permission request. But for that I'll need to know his/her user id so I can access the info via graph API.</p>
  
  <p>The idea is to do it when he/she is visiting for the first time my page app.
  <a href="http://apps.facebook.com/xxxxxxxxxxxxxxx" rel="nofollow">http://apps.facebook.com/xxxxxxxxxxxxxxx</a></p>
  
  <p>Any idea?</p>