Javascript calls C# code and parser error

I am trying to get my javascript to call some C# code that I have added to my Sharepoint site. Unfortunately every time it runs, I’m not getting the “Success” i had programmed in. Instead I get this:

My Javascript code:

function test() {     
             $.ajax({
             type: "POST",
             url: 'NewForm.aspx/doThis',
             data: "",
             contentType: "application/json; charset=utf-8",
             dataType: "json",
             success: function (msg) {
                alert("Success");
             },
             error: function (XMLHttpRequest, textStatus, errorThrown) {
                 alert("Request: " + XMLHttpRequest.toString() + "nnStatus: " + textStatus + "nnError: " + errorThrown);
             }
         });
     };

And My C# code:

    [WebMethod]                                
 public static void doThis()
{
  //Code
}

The code is not supposed to do anything yet, but print out success if it was able to get to the method.