You must be making that mistake:

That is, failure to authenticate, to get around such problem goes in the folder App_Start, open the file RouteConfig.cs and left so, being that in the second line put as RedirectMode.Off
public static class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
       var settings = new FriendlyUrlSettings();
       settings.AutoRedirectMode = RedirectMode.Off;
       routes.EnableFriendlyUrls(settings);
    }
}
Ready will work immediately.

A tip: make a WebService.asmx:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
namespace WebApplication2
{   
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)] 
    [System.Web.Script.Services.ScriptService]
    public class WebServiceDados : System.Web.Services.WebService
    {
        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World";
        }
        [WebMethod()]
        public List<string> MontarGrafico()
        {
            var l = new List<string>();
            l.Add("teste1");
            l.Add("teste2");
            return l;
        }
    }
}
Javascript Ajax:
$.ajax({
        type: "POST",
        url: "WebServiceDados.asmx/MontarGrafico",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (produtos) {
            var prods = produtos.d;
            $.each(prods, function (index, prod) {
                alert(prod);
            });                
        }
});
In this mode you don’t need to touch that setting RouteConfig.cs
Another point to note is the sending and receiving, configure your jsonSerialization on your Webconfig, to receive/send data with large sizes
<configuration> 
   <system.web.extensions>
       <scripting>
           <webServices>
               <jsonSerialization maxJsonLength="50000000"/>
           </webServices>
       </scripting>
   </system.web.extensions>
</configuration> 
Note: to check the errors I install the Firebug Lite, a widely used plugin that picks errors Javascript by browser.
							
							
						 
I added Webservice.asmx, and it worked. How do I view that part of the Post? The print you put up?
– Diego Zanardo
I use a plugin in google Chrome Firebug Lite: https://getfirebug.com/firebuglite
– user6026