Modal Popup Extender

Question

Hi.
 I have a modal popup extender in my page.i want 2 display the popup in my page loads.
I have write some codes for it.bt it doesnt working.
My code is as follows
<asp:Button ID="Button1" runat="server" Text="" style="display:none" />
<cc1:modalpopupextender id="ModalPopupExtender1" backgroundcssclass="modalBackground" BehaviorID="modalpopup"
runat="server" cancelcontrolid="btnCancel" okcontrolid="btnOkay" targetcontrolid="Button1"
popupcontrolid="Panel1" drag="true" popupdraghandlecontrolid="PopupHeader">
</cc1:modalpopupextender>
<div id="Panel1" style="display: none;" class="pnlPop">
<div >
<div id="PopupHeader">
<div >
Warnning Popup Header</div>
<div >
</div>
</div>
<div >
<p>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</p>
</div>
<div style="display:none">
<input id="btnOkay" value="Done" type="button" />
<input id="btnCancel" value="Cancel" type="button" />
</div>
</div>
</div>
 
Style used for this code is:
<style type="text/css">
.modalBackground
{
background-color: #414141;
filter: alpha(opacity=70);
opacity: 0.7;
}
.pnlPop
{
background-color: #FFFFFF;
font-family: Tahoma, Helvetica, Sans-Serif;
font-weight: normal;
font-size: 11px;
padding: 5px;

}


</style>
And Script for this is:
<script type="text/javascript">
function pageLoad() {
ShowPopup();
setTimeout(HidePopup, 10000);
}
function ShowPopup() {
$find('modalpopup').show();
}
function HidePopup() {
$find('modalpopup').hide();
}
</script>
 
Please help me
Thanks in advance..