Q1000 Once an image has loaded how can I display its width and height beneath the image?

<script language="JavaScript"><!--
function update(what) {
    document.myForm.width.value = what.width;
    document.myForm.height.value = what.height;
}
//--></script>

<img src="image.gif" onLoad="update(this)">

<form name="myForm">
<input type="text" name="width">
<input type="text" name="height">
</form>