JavaScript DHTML/Document/all
Check if a tag exists
<html>
<head>
<title>A Simple Page</title>
<script language="JavaScript">
function findhead1()
{
var detectElement = document.all("head1");
if (detectElement == head1)
{
alert("Element \"head1\" exists");
}
}
</script>
</head>
<body onload="findhead1()">
<h1 id="head1">Heading One</h1>
</body>
</html>