title: What is the X-FB-DEBUG header returned from Facebook?
body: <p>I'm wondering what the header mentioned above is. It's included in the response when I do JSONP calls to Facebook, or even when I simply access <a href="http://static.ak.fbcdn.net/" rel="noreferrer">http://static.ak.fbcdn.net/</a></p>
  
  <p>I haven't found any documentation on facebook, e.g. on <a href="https://developers.facebook.com/docs/reference/ads-api/etags-reference/" rel="noreferrer">https://developers.facebook.com/docs/reference/ads-api/etags-reference/</a></p>
  
  <p>So, hope somebody can help me. thx!</p>