<script type="text/javascript">
  function goFullscreen(id) {
    // Get the element that we want to take into fullscreen mode
    var element = document.getElementById(id);
    
    // These function will not exist in the browsers that don't support fullscreen mode yet, 
    // so we'll have to check to see if they're available before calling them.
    
    if (element.mozRequestFullScreen) {
      // This is how to go into fullscren mode in Firefox
      // Note the "moz" prefix, which is short for Mozilla.
      element.mozRequestFullScreen();
    } else if (element.webkitRequestFullScreen) {
      // This is how to go into fullscreen mode in Chrome and Safari
      // Both of those browsers are based on the Webkit project, hence the same prefix.
      element.webkitRequestFullScreen();
   }
   // Hooray, now we're in fullscreen mode!
  }
</script>

<img class="video_player" src=http://www.mamicode.com/"image.jpg" id="player">>

这样就可以实现全屏显示了，但是DOM元素的尺寸不会改变。别担心，下面会帮你解决这个问题。

<style type="text/css">
  .player:-webkit-full-screen {
    width: 100%;
    height: 100%;
  }
  .player:-moz-full-screen {
    width: 100%;
    height: 100%;
  }
</style>
<img class="video_player" src=http://www.mamicode.com/"image.jpg" id="player3">>

这样对大部分DOM元素都起作用，但是对于iframe元素，还需添加allowFullScreen这个属性。
<iframe src=http://www.mamicode.com/"iframe_src.html" width="400" height="300" allowFullScreen></iframe>

ok,大功告成！
reference: http://www.jwplayer.com/blog/using-the-browsers-new-html5-fullscreen-capabilities/


DOM元素全屏显示解决方案