<!DOCTYPE html>
<!--
 | The "vw" equal to 1% of the width of the initial containing block.
 | The "vh" equal to 1% of the height of the initial containing block.
 |   https://www.w3.org/TR/css3-values/#viewport-relative-lengths
 | This test only passes when viewport is 640 x 360.
 -->
<html>
<head>
  <style>
    body {
      font-family: roboto;
    }
    div {
      width: 50vw;
      height: 50vh;
      font-size: 5vw;
      background-color: #00F;
    }
  </style>
</head>

<body>

<div>
  Width, height and font-size are of vw, vh units.
</div>

</body>
</html>