title: How do I tell srcset attribute to load NO images when viewport smaller than certain size
body: <p>I'm having trouble understanding how to keep <code>srcset</code> from loading any images on screens &lt; <code>768px</code>. </p>
  
  <p>I've tried the code below but the sizes attribute doesn't seem to do what you may think. 
  Below loads <code>1024.jpg</code> on all screen sizes:</p>
  
  <pre><code>&lt;img 
    src="default.jpg"
    srcset="img/1024.jpg 1024w" 
    sizes="(min-width: 768px) 768px, 100vw"
  /&gt;
  </code></pre>
  
  <p>Or the picture element, if it would honor an <a href="http://jsfiddle.net/BenRacicot/crjym91h/" rel="noreferrer">empty srcset</a> but it only "hints" to which image a browser should load.</p>