hiddenfield value lost on PostBack

 Hi
I have a hiddenfield, which I want to save the scroll position of asp.panel scrollbar during postback, and when during postback this value is called back to set the scroll position.
Using javascript I can grab the value from the scrollbar, and assign it to the hidden field, but when I post the page back the value has gone.
Here is my code snippet:
<script type="text/javascript" language="javascript">
 
function SetScroll(val) {
alert(document.getElementById('div1').childNodes('ScrollPos').value);
 
}
function ScrollTo(what) {
var test = what.split('/');
document.getElementById(test[0]).scrollTop = document.getElementById('div1').childNodes('ScrollPos').value;
}
 
</script>
<div id="div1" cl ...