StudioPress Community Forums - IE8 JavaScript Error

Can someone please tell me why I continually get this JavaScript error with IE8. The page loads correctly but it always shows this error:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0)
Timestamp: Mon, 22 Jun 2009 02:18:10 UTC

Message: 'document.getElementById(...)' is null or not an object
Line: 52
Char: 2
Code: 0
URI: http://thegreatmonkey.com/

Here is the code from my site:

Code:

-->

</style>

 

<script type="text/javascript"><![CDATA[//><!--

sfHover = function() {

        if (!document.getElementsByTagName) return false;

        var sfEls = document.getElementById("nav").getElementsByTagName("li");

 

        for (var i=0; i<sfEls.length; i++) {

                sfEls[i].onmouseover=function() {

                        this.className+=" sfhover";

                }

                sfEls[i].onmouseout=function() {

                        this.className=this.className.replace(new RegExp(" sfhover\\b"), "");

                }

        }

 

}