<!DOCTYPE html>
<html>
    <head>
        <script type="text/javascript">
            function runTest() {
                document.getElementById('testMenclose').removeAttribute("notation");
            }
        </script>
    </head>
    <body onload="runTest()">
        <p>
            <math><menclose id="testMenclose" notation="box"><mspace width="100px" height="50px" mathbackground="red"></mspace></menclose></math>
		</p>
    </body>
</html>