Sorry about, I review the sample again and modified some place, it work now. thank you guy.
WebForm8_Child.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm8_Child.aspx.cs" Inherits="WebApplication1.WebForm8_Child" %>
<%@ Register assembly="Coolite.Ext.Web" namespace="Coolite.Ext.Web" tagprefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<ext:ScriptManager ID="ScriptManager1" runat="server" />
<div style="height: 663px">
<div style="height: 266px">
<ext:Label ID="Label1" runat="server" Text="This is header of Panel1" />
<ext:Panel runat="Server" ID="Panel2" AutoScroll="true" Title="Panel2" Height="81px">
<Body>
<ext:Button ID="Button1" runat="server" Text="1" />
<ext:Button ID="Button2" runat="server" Text="2" />
<ext:Button ID="Button3" runat="server" Text="3" />
<ext:Button ID="Button4" runat="server" Text="4" />
<ext:Button ID="Button5" runat="server" Text="5" />
<ext:Button ID="Button6" runat="server" Text="6" />
<ext:Button ID="Button7" runat="server" Text="7" />
<ext:Button ID="Button8" runat="server" Text="8" />
<ext:Button ID="Button9" runat="server" Text="9" />
<ext:Button ID="Button10" runat="server" Text="10" />
<ext:Button ID="Button11" runat="server" Text="11" />
<ext:Button ID="Button12" runat="server" Text="12" />
<ext:Button ID="Button13" runat="server" Text="13" />
<ext:Button ID="Button14" runat="server" Text="14" />
<ext:Button ID="Button15" runat="server" Text="15" />
<ext:Button ID="Button16" runat="server" Text="16" />
</Body>
</ext:Panel>
<ext:Label ID="Label2" runat="server" Text="This is tail of Panel1" />
</form>
</body>
</html>
WebForm8.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm8.aspx.cs" Inherits="WebApplication1.WebForm8" %>
<%@ Register assembly="Coolite.Ext.Web" namespace="Coolite.Ext.Web" tagprefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<ext:ScriptManager ID="ScriptManager1" runat="server" />
<ext:TabPanel ID="Panel1" runat="Server" Height="663px">
<Tabs>
<ext:Tab AutoScroll="false">
<AutoLoad Mode="IFrame" Url="WebForm8_Child.aspx"></AutoLoad>
<Body>
</Body>
</ext:Tab>
</Tabs>
</ext:TabPanel>
</form>
</body>
</html>
Huang Yes