//UpdatePanel BusyIndicator
    // gif:     http://www.ajaxload.info
    // html:      <span id="busyIndicator" class="floatRight"></span>
    // #busyIndicator        {width:16px; height:16px;}
    // .busy            {background:transparent url(../Images/ajax-loader.gif) no-repeat scroll left top;}
    
var prm = Sys.WebForms.PageRequestManager.getInstance();
prm.add_initializeRequest(InitializeRequest);
prm.add_endRequest(EndRequest);
 
function InitializeRequest(sender, args) {
    $("#busyIndicator").addClass("busy");
}
 
function EndRequest(sender, args) {
    $("#busyIndicator").removeClass("busy");
}