.blur
{
background-color: White;
filter: alpha(opacity=50);
opacity: 0.7;
z-index: 120;
}
<asp:UpdateProgress ID="UpdateProgress2" runat="server" >
<ProgressTemplate>
<div id="Imgt" style="position: absolute;width:1030px; height:300px;" align="center" valign="middle" runat="server" class="blur">
<img src="ajax-loader (5).gif" style="position:relative;right:100px" /><br />
</div>
</ProgressTemplate>
</asp:UpdateProgress>