<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width">
    <title>Responsive HTML images demo</title>
    <style>

      img {
        width: 320px;
      }

    </style>
  </head>
  <body>
    

        <img srcset="elva-fairy-320w.jpg,
                     elva-fairy-480w.jpg 1.5x,
                     elva-fairy-640w.jpg 2x"
             src="elva-fairy-640w.jpg" alt="Elva dressed as a fairy"> 

        
  </body>
</html>