iFrames and their src's

why does this…


<script language="javascript">
<!--

function showFactsheets()
{
	
	document.getElementById("doclib_iFrame").src = "factsheets.html";
}

//-->
</script>
</head>

<body>
<a href="#" onclick="showFactsheets()">Factsheets</a>
<br /><br />

<iframe id="doclib_iFrame">

</iframe>

</body>

give me the error message

“Object Expected”

:huh: