My web site working fine but at one place show error given below

Server Error in '/' Application.
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable.  Please review the following URL and make sure that it is spelled correctly. 

Requested URL: /Operation/null

$('.save').on('click', function (e) {
       var tr = $(this).parents('tr:first');
       var NewID = tr.find("#newID").html();
        e.preventDefault();
       if (NewID != "") {
           var DataObjectForAjaxCall = { strBooking: NewID };
           $.ajax({
               url: "@Url.Action("invoicePrint", "Return", new { area = "Operation" })",
               method: "GET",
               data: DataObjectForAjaxCall,
               cache: false,
               async: false,
               success: function (Result) {
                   alert(Result);
                   var w = window.open($(this).parent().data("url"));
                   $(w.document.body).html(Result);
               }
           });
       }
       else {
           msgAlerts(Result);
       }
   });

public ActionResult invoiceShipment(string strBooking)
       {
           if (strBooking != "")
           {
               int Intid = Convert.ToInt32(strBooking) - 120000000;
               BookShipmet objBS = new BookShipmet();
               objBS = new BL_Operation().GetShipmentByID(Intid);
               return PartialView("~/Areas/Operation/Views/Shared/Return/_invoicePrint.cshtml", objBS);
           }
           else
           {
               return RedirectToAction("Index", "TimeOutError");
           }
           //return View();
       }