<!-- Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/ -->
<html>
<head>
  <title>variables test</title>
  <style>
    :root {
      --10: 10px;
      ---blue: blue;
    }
    #a {
      font-size: var(--10);
    }
    #b {
      color: var(---blue);
    }
  </style>
</head>
<body>
  <div id="a">A</div><br>
  <div id="b">B</div>
</body>
</html>
