its related to modalpopupextender

sir i want to show panel on the click of linkbutton, that linkbutton is used in the gridview.

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="MakePayment.aspx.cs" Inherits="Salary_MakePayment" %>

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
<style type="text/css">
.modalBackground
{
background-color: Gray;
filter: alpha(opacity=70);
opacity: 0.7;
cursor: wait;
}
.modalPopup
{
background-color: #EEEEEE;
border-width: 3px;
border-style: solid;
border-color: Gray;
font-family: Verdana;
font-size: medium;
padding: 3px;
width: 595px;
}
.parentDisable
{
z-index: 999;
width: 100%;
height: 100%;
display: none;
position: absolute;
top: 0;
left: 0;
background-color: #000;
color: #aaa;
opacity: .9;
filter: alpha(opacity=50);
}
#popup
{
width: 300;
height: 300;
position: relative;
color: #000;
background-color: #fff;
top: 25%;
background-image: url(catbg-1.gif);
}
</style>

<script type="text/javascript" language="javascript">
function pop(div) {
document.getElementById(div).style.display = 'block';
//return false
}

function hide(div) {
document.getElementById(div).style.display = 'none';
//return true
}
</script>



<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">

<table>
<tr>
<td>
From Date
</td>
<td>
<asp:TextBox ID="txtFromDate" runat="server">

<asp:CalendarExtender ID="txtFromDate_CalendarExtender" runat="server"
Enabled="True" TargetControlID="txtFromDate">


</td>
<td>
To Date
</td>
<td>
<asp:TextBox ID="txtToDate" runat="server">
<asp:CalendarExtender ID="txtToDate_CalendarExtender" runat="server"
Enabled="True" TargetControlID="txtToDate">

</td>
</tr>
<tr>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
<asp:Button ID="btnSearch" runat="server" Text="Search"
onclick="btnSearch_Click"/>
</td>
</tr>
</table>

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<contenttemplate>
<asp:GridView ID="gv_Result" runat="server" AutoGenerateColumns="False">

<columns>
<asp:TemplateField HeaderText="Employee Code">
<itemtemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("emp_code") %>'>

<edititemtemplate>
<asp:Tex