title: how to use alternate content for <video> element
body: <p>I mean what should i do so as not to display video files missing in a database row? I am new to php and this is my code.</p>
  
  <pre><code>&lt;video width="100%" controls preload="auto"&gt;
   &lt;source src="postfiles/&lt;?php echo $res['file']; ?&gt;" 
     type='video/webm;codecs="vp8, vorbis"' /&gt;
   &lt;source src="postfiles/&lt;?php echo $res['file']; ?&gt;"
     type='video/mp4;codecs="avc1.42E01E, mp4a.40.2"'/&gt;
  &lt;/video&gt;
  </code></pre>