title: Error message after install custom apps
body: <p>I followed the instruction and replace  the apps id and url.</p>
  
  <p><a href="https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID" rel="nofollow">https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID</a>
  &amp;display=popup&amp;next=YOUR_URL</p>
  
  <p>Then i add this apps in one of my page.In my page im getting an error
  "Not Found</p>
  
  <p>The requested URL /opg/index1.html/ was not found on this server.</p>
  
  <p>Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."</p>
  
  <p>How should i rectify this error?</p>