etAttribute('role', input.value);
              html.setAttribute('role', input.value);
              head.setAttribute('role', input.value);
              output.innerHTML = 'role ' + input.value + ' added to body, html and head elements';
            });
          </script>
				</div>
        <p>Expectation: conformance checkers will indicate that <code>role=document</code> is redundant on <code>html</code> element, and that a <code>role</code> with any other value is invalid on the <code>html</code> elem