title: Facebook session expiration error when try to post actions to open graph  using 'App access token'
body: <p>I am facing this error with some of my users, the case is as following:</p>
  
  <p>I use facebook "App access token" to post actions to facebook Open Graph instead of the user access token because app access token don't expire according to facebook documentation unless you refreshed the app secret, I use the follwoing Post url to post actions </p>
  
  <p><a href="https://graph.facebook.com/user_facebook_id/App_Namespace:action_name?FBOG_Object=FBOG_OBJECT_URL&amp;access_token=app_access_token" rel="nofollow">https://graph.facebook.com/user_facebook_id/App_Namespace:action_name?FBOG_Object=FBOG_OBJECT_URL&amp;access_token=app_access_token</a></p>
  
  <p>Some of the actions do appear on facebook, but for some users the actions fails to post and return the following message:</p>
  
  <pre><code>{ "error": { "message": "Error validating access token: Session has expired at unix time 1345759200. The current unix time is 1345925578.", "type": "OAuthException", "code": 190, "error_subcode": 463 } } 
  </code></pre>
  
  <p>What am I doing wrong? Why do I have an expiration error although am using the app access token? Should I worry for user permissions?</p>