title: Javascript - Detect Youtube Default-Thumbnail
body: <p>Is there any way to see if a Youtube Thumbnail really exists or Youtube just replaced it by the default thumbnail?</p>
  
  <p>For example, a video without this thumbnail : <a href="http://img.youtube.com/vi/G75WApUdYJ4/maxresdefault.jpg" rel="noreferrer">http://img.youtube.com/vi/G75WApUdYJ4/maxresdefault.jpg</a>
  And one with an existing thumbnail : <a href="http://img.youtube.com/vi/pkyLAWX5V30/maxresdefault.jpg" rel="noreferrer">http://img.youtube.com/vi/pkyLAWX5V30/maxresdefault.jpg</a></p>
  
  <p>Story:
  I just tried to use Youtube's maxresdefault-Thumbnails as background for my "Media-Player-Page".
  Using normal images works fine but for any reasom some Youtube Videos don't have a maxresdefault-Thumbnail. If i load this image I just get the small default Thumbnail which isn't really enjoyable on a FullHD Screen.</p>