can not execute outerHTML On Mozilla! (JavaScript)

The following JavaScript code can run on IE.
But can not run on Mozilla!
How can I do?

<input id=aaa type=button value=test onclick=f_go()>
<script>
function f_go()
{
document.getElementById('aaa').outerHTML='<textarea></textarea>'
}
</script>

Try this:

<input id="aaa" type="button" value="test" onclick="f_go()">
<script>
function f_go()
{
document.forms['myform'].elements['aaa'].value="";
}
</script>