New <picture> tag markup.

picture-tag.html

<picture>

  <!-- Source for every width below 480px -->
  <source src="http://bukk.it/i-approve.png" media="max-width: 480px;">

  <!-- Source for widths between 480px and 800px -->
  <source src="http://bukk.it/hedgehog.jpg" media="min-width: 480px; max-width: 800px;">

  <!-- Source for all widths above 800px -->
  <source src="http://bukk.it/facepalm.jpg" media="min-width: 800px;">

  <!-- Image placeholder. In legacy it will be populated by polyfill,
       browsers that support <picture> will ignore. -->
  <img src ="">
   
  <!-- Load this image if no JS support is present -->
  <noscript>
    <img  src="http://bukk.it/facepalm.jpg">
  </noscript>

</picture>