title: Facebook Graph API returns 403 Forbidden
body: <p>I'm having a problem using graph API. 
  My program worked perfectly until two months ago. 
  And yesterday I ran my program, and it suddenly fails to call graph API. 
  My server uses HttpPost object to make httpPost request. 
  When I copy-paste the exact same request URL to the web browser, it receives corrent JSON response,(so I don't think a token or url is the problem) but when it comes to HttpPost, it fails and get HTTP/1.1 403 Forbidden response. </p>
  
  <p>I may have changed my server configuration, but I can't remember. Has Graph API changed for last two months? I need help. </p>
  
  <p>Any idea?</p>