title: Why does verifying a Facebook access token sometimes result in a 400 response?
body: <p>Our users can give us permission to do offline posts for them.  We have them log into their Facebook account via a popup Facebook login, and they grant us these permissions: publish_stream, offline_access, manage_pages</p>
  
  <p>We fetch an access token.</p>
  
  <p>We fetch a list of wall &amp; fan pages and associated access tokens to which the user has administrative access via:</p>
  
  <pre><code>https://graph.facebook.com/me/accounts?access_token=[access token]
  </code></pre>
  
  <p>Our user chooses which Facebook pages for us to post to, and we store the associated Facebook user id , page/wall names and access tokens</p>
  
  <p>Prior to posting a message to the user's wall / fan page(s), we verify that the associated access tokens are still valid:</p>
  
  <pre><code>https://graph.facebook.com/[facebook user id]/?access_token=[access token]
  </code></pre>
  
  <p>Most of the time, this results in a response where we can parse out whether or not the access_token was accepted.  Occasionally, however, Facebook responds with a 400.</p>
  
  <p>Any ideas on why we sometimes get a 400 response?</p>