<!DOCTYPE html>
<html>
<head>
  <title>background-size: 100% 100%; stretch reference</title>
  <style type="text/css">
#outer
{
  border: 10px solid black;
  width: 60px;
  height: 120px;
}
#inner1
{
  background: blue;
  width: 15px;
  height: 120px;
  display: inline-block;
  background-image: url(blue-16x20.png);

  /* obscure sampling artifacts at the color boundary */
  border-right: 5px solid black;
}
#inner2
{
  background: lime;
  width: 35px;
  height: 120px;
  display: inline-block;
  background-image: url(green-16x20.png);

  /* obscure sampling artifacts at the color boundary */
  border-left: 5px solid black;
}
  </style>
</head>
<body>
<div id="outer"><div id="inner1"></div><div id="inner2"></div></div>
</body>
</html>