Exception in folder tree stucture in jstree

I'm trying to create a tree structure in jstree. Infact i have done it successfully during testing(as a sample app).

But when I integrated it with the web project I'm working on it gives an exception.It doesn't even display the folders as a structure I can't figure our why

This is the exception i'm getting

uncaught exception: TypeError: contentWindow.document.getElementsByTagName("head")[0] is undefined

this is my code

<script type="text/javascript" src="_lib/sarissa.js"></script>
<script type="text/javascript" src="_lib/sarissa_ieemu_xpath.js"></script>
<script type="text/javascript" src="_lib/jquery.xslt.js"></script

<div id="demo1"开发者_开发百科 style="width:200px;">
    <ul>
        <li id="phtml_1">
            <a href="#">Root node 1</a>
            <ul>
                <li id="phtml_2">
                    <a href="#">Child node 1.1</a>
                </li>
                <li id="phtml_3">
                    <a href="#">Child node 2.2</a>
                </li>
            </ul>
        </li>
        <li id="phtml_4">
            <a href="#">Root node 2</a>
                <ul>
                <li id="phtml_2">
                    <a href="#">Child node 2.1</a>
                </li>
                <li id="phtml_3">
                    <a href="#">Child node 2.2</a>
                </li>
            </ul>
        </li>
        <li id="phtml_4">
            <a href="#">Root node 3</a>
        </li>
    </ul>
</div>
<div id="value"></div>
<script type="text/javascript">
$(function () {

    $("#demo1").jstree({        
    }).bind("loaded.jstree", function (event, data) {               
    }); 

});
</script>

I would be glad if someone could help me out.

thanks in advance