var asyncPostBackErrorMessage = "";
var pageReqMan = Sys.WebForms.PageRequestManager.getInstance();

pageReqMan.add_beginRequest(BeginAsyncPostBackRequestHandler);
pageReqMan.add_endRequest(EndAsyncPostBackRequestHandler);

function BeginAsyncPostBackRequestHandler(sender, args)
{
    var errorPlaceHolder = $get("errorPlaceHolder");

    if (errorPlaceHolder)
    {
        errorPlaceHolder.style.visibility = "hidden";
    }
}

function EndAsyncPostBackRequestHandler(sender, args)
{
    var strReturn = "\n"; //"<br />";
    var errorPlaceHolder = $get("errorPlaceHolder");
    
    args.set_errorHandled(true);

    if (errorPlaceHolder)
    {
        if (args.get_error())
        {
            asyncPostBackErrorMessage = args.get_error().message;
            
            errorPlaceHolder.style.visibility = "visible";
            
            //    alert ("Message: " + args.get_error().message + strReturn +
            //        "Name: " + args.get_error().name + strReturn +
            //        "Description: " + args.get_error().description + strReturn +
            //        "Http Status: " + args.get_error().httpStatusCode + strReturn +
            //        "popStackFrame: " + args.get_error().popStackFrame + strReturn);
        }
        else
        {
            errorPlaceHolder.style.visibility = "hidden";
        }
    }
}