<!DOCTYPE html>
<html lang="en-US">
<head>
  <title>border-image-width: 2em</title>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  <meta http-equiv="Content-Style-Type" content="text/css">
  <style type="text/css">
  div {
    border-width: 1em;
    border-style: solid;
    border-image: url('3x3green-1DD813.png') 1 1 1 1 / 2em;
  }
  </style>
</head>
<body>
<div>
border.png<br />second longer longer longer longer longer longer line<br />third longer longer longer longer longer longer line
</div>
</body>
</html>