<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
        <ProgressTemplate>
        <asp:Panel ID="pnlBackGround" runat="server" CssClass="popup-div-background">
            <div id="divFeedback" runat="server" class="popup-div-front">
                <img src="../Images/ajax-loader.gif" border="0" />
                The request is being processed. Please wait...<br />
                This window will disappear when the process is finished.
            </div>
        </asp:Panel>
        </ProgressTemplate>
    </asp:UpdateProgress>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
       <div>
        <div class="clear-div"></div>
        <div class="section-heading">
            <asp:Label ID="lblPageTitle" runat="server" EnableViewState="false">AJAX Update Progress</asp:Label>
        </div>
        <div class="section-information">
        <div class="clear-div"></div>
        <asp:Label ID="lblResults" runat="server" EnableViewState="false" Visible="false"></asp:Label>
        <asp:Button ID="btnProcess" runat="server" Text="Process" OnClick="btnProcess_Click" />
            <br />
        </div>
    </div>
        </ContentTemplate>
    </asp:UpdatePanel>

    Protected Sub btnProcess_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
        For i As Integer = 0 To 10
            Me.lblResults.Text += DateTime.Now.ToString() & "<br />"
            Threading.Thread.Sleep(1000)
        Next
        Me.lblResults.Visible = True
    End Sub

.popup-div-background
{
    position:absolute;
    top: 0;
    left: 0;

    background-color:#ccc;
    filter:alpha(opacity=90);
    opacity:0.9; 

    /* the following two line will make sure
    /* that the whole screen is covered by
    /* this transparent layer */

    height: 100%;
    width: 100%;
    min-height: 100%;
    min-width: 100%
}
.popup-div-front
{
    background-color: #ffffff;
    color: black;
    width: 70%;
    text-align: left;
    vertical-align: middle;
    position: absolute;
    top: 5%;
    left: 15%;
    bottom:5%;
    font-weight:bold;
    padding: 10px 5px 5px 5px;
    font-family:Verdana;
}