I have tested following code and its working fine..
here the tested code..
<asp:ScriptManager ID="s1" runat="server">
</asp:ScriptManager>
<asp:UpdateProgress ID="up1" runat="server" AssociatedUpdatePanelID="u1">
<ProgressTemplate>
<img src="images/progress.gif" alt="processing.."/>
</ProgressTemplate>
</asp:UpdateProgress>
<asp:UpdatePanel ID="u1" runat="server">
<ContentTemplate>
<asp:Panel ID="Panel1" runat="server">
<table align="left" border="1" width="100%">
<tr>
<td align="center" colspan="2">
<asp:Label ID="Label2" runat="server" Text="Your Message to Top Management" Font-Size="Large"
ForeColor="Black"></asp:Label>
</td>
</tr>
<tr>
<td align="left">
<asp:Label ID="Label1" runat="server" Text="Write Your Message" Font-Size="Medium"
ForeColor="Black"></asp:Label>
</td>
<td align="left">
<asp:TextBox ID="txt_msg" runat="server" TextMode="MultiLine" Height="200px" Width="500px"
Font-Size="Medium"></asp:TextBox>
</td>
</tr>
<tr>
<td colspan="2">
</td>
</tr>
<tr>
<td colspan="2" align="center">
<asp:Button ID="Button1" runat="server" Text="Send Your Message"
OnClick="Button1_Click" Font-Size="Large" />
</td>
</tr>
<tr>
<td align="center" colspan="2">
<asp:Label ID="Label3" runat="server" Font-Size="Large" ForeColor="Green" Visible="false"></asp:Label>
</td>
</tr>
</table>
</asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
check out following link for more understanding..
http://msdn.microsoft.com/en-us/library/bb386421.aspx[
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