Please try following code where I have modified table in update progress bar
<asp:updatepanel id="UpdatePanel1" runat="server" xmlns:asp="#unknown">
<contenttemplate>
<asp:label id="Label99" runat="server" width="145px"></asp:label>
</contenttemplate>
<triggers>
<asp:asyncpostbacktrigger controlid="Button4" eventname="Click" />
</triggers>
</asp:updatepanel>
<asp:updateprogress id="UpdateProgress1" associatedupdatepanelid="UpdatePanel1" runat="server" xmlns:asp="#unknown">
<progresstemplate>
<table cellspacing="1" class="style56w" runat="server" id="table76">
<tr>
<td>
<asp:image id="Image21" runat="server" descriptionurl="~/images/updateprogress.gif"
Height="60px" ImageUrl="~/images/updateprogress.gif" Width="20px" BackColor="White"/>
</asp:image></td>
</tr>
</table>
</progresstemplate>
</asp:updateprogress>
write using in code behind file
using System.Web.UI.HtmlControls;
after that you can access your table in code behind file
HtmlTable table = UpdateProgress1.Controls[0].FindControl("table76") as HtmlTable;
table.Style.Add(HtmlTextWriterStyle.Top, "1140px");