add title to ajax extender popup

example

<asp:scriptmanager id="ScriptManager1" runat="server">
</asp:scriptmanager>

<asp:button id="Button1" runat="server" text="Button" />

<cc1:modalpopupextender id="ModalPopupExtender1" runat="server"
cancelcontrolid="btnCancel" okcontrolid="btnOkay"
targetcontrolid="Button1" popupcontrolid="Panel1"
popupdraghandlecontrolid="PopupHeader" drag="true"
backgroundcssclass="ModalPopupBG">
</cc1:modalpopupextender>

<asp:panel id="Panel1" style="display: none" runat="server">
<div class="HellowWorldPopup">
                <div class="PopupHeaderClasss" id="PopupHeader">Header</div>
                <div class="PopupBody">
                    <p>This is a simple modal dialog</p>
                </div>
                <div class="Controls">
                    <input id="btnOkay" type="button" value="Done" />
                    <input id="btnCancel" type="button" value="Cancel" />
</div>
        </div>
</asp:panel>

<style>

.PopupHeaderClasss{
padding: 0.3em 0.1em;
 text-align: left;
 border:solid 1px black;
 background-color: #5871c3;
 font-weight:bold;
    }

</style>