fieldset-add-invalid-barred.html

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<!DOCTYPE html>

<!-- fieldset with invalid barred for constraint validation element -->

<html>

  <head>

    <style>

      fieldset:valid { display: none ;}

    </style>

    <script>

      function onloadHandler()

        document.getElementById("fieldset").appendChild(document.getElementById('i'));

        document.documentElement.className = '';

    </script>

  </head>

  <body onload="onloadHandler();">

    <input required readonly id="i">

    <fieldset id="fieldset">

    </fieldset>

  </body>

</html>