<!DOCTYPE HTML>
<title>multi-background-clip-content-border-ref</title>
<style>
  div#outer { background-image: url(green-16x20.png);
              width: 100px; height: 100px;
              border: 20px solid transparent; }
  div#inner { background-image: url(aqua-32x32.png);
              width: 100%; height: 100%; }
</style>
<div id="outer"><div id="inner"></div></div>