title: Possible to test if user blocked his wall
body: <p>I using FB.api feed method in ordr to publish some messages in user's wall with my facebook application.</p>
  
  <p>The problem is, when an user block his wall, in order to have the good fb popup i obtain the popup with the title "Error whith publishing" and the message "Cannot post to user's Wall".</p>
  
  <p>Is it possible to test if an user blocked his wall?
  Or is it possible to get an error from facebook and do another things?</p>
  
  <p>Thanks :-).</p>