i want to display time using hidden variable in a page,but
when i click button that page that hidden variable loosing
its value.i m sending the code also.

<script type="text/javascript" language="javascript">
var tick=0;

window.onload = function() {
//debugger

if(document.getElementById("hdnTicker").value != "")

tick =
parseInt(document.getElementById("hdnTicker").value);
setInterval("Timer()",1000);


}

function Timer()
{
//debugger
document.getElementById("hdnTicker").value = tick++;
//alert(document.getElementById("hdnTicker").value);

document.getElementById("lblTimeSpent").innerHTML = "0." + tick;
if(tick == 30)
{
//message or redirect to result window
alert('time is out');
//clearTimeout();
}
} </script>


<form id="form1" runat="server">
<div>
<table>
<tr>
<td>
<asp:Label ID="lblTimeSpent" runat="server"
Visible="true" ForeColor="Blue" ></asp:Label>
</td>

<td>
<%-- <asp:textbox EnableViewState="true"
id="hdnTicker" runat="Server"
style="visibility:hidden"></asp:textbox>--%>
</td>
</tr>
<tr>
<td>
<asp:Button ID="btn" runat="server"
Text="hi" OnClick="btn_Click" Height="30px" Width="60px" />
</td>
</tr>
</table>




<%--<asp:HiddenField ID="txt" runat="server"
Visible="true" />--%>

</div>
</form>
<input type="hidden" id="hdnTicker" name="hdnTicker"
enableviewstate="true" runat="server" />