Maintain Scroll Position of ASP.NET Panel after postback

<script language="javascript" type="text/javascript">
var IsPostBack= '<%=IsPostBack.ToString() %>';
window.onload = function(){
var strCook = document.cookie;
if(strCook.indexOf("!~")!=0){
var intS = strCook.indexOf("!~");
var intE = strCook.indexOf("~!");
var strPos = strCook.substring(intS+2,intE);
if (IsPostBack=='True')
{
document.getElementById("<%=pnlTree.ClientID %>").scrollTop = strPos;
}
else
{
document.cookie = "yPos=!~0~!";
}
}
}
function SetDivPosition(){
var intY = document.getElementById("<%=pnlTree.ClientID %>").scrollTop;
document.title = intY;
document.cookie = "yPos=!~" + intY + "~!";
}

    </script>

<asp:Panel ID="pnlTree" runat="server" Height="462px" Width="390px" ScrollBars="Auto" onscroll="SetDivPosition()">
….
</asp:Panel>