title: Ajax call. Always return error
body: <p>Get stacked with ajax call.
  I'm allways getting error. I've tried to return from server ArrayList because i have some scheme in some my projects. But the result was same. Json is valid. Staus 200 OK and permanent error.</p>
  
  <p>Here is my client-side code</p>
  
  <pre><code>$.ajax({
          type: "POST",
          url: "services.aspx/GetHexString",
          data: "{'strGetParamsString':'LYALYA'}",
          contentType: "application/json; charset=utf-8",
          dataType: "json",
          success: function(msg) {
              alert(msg.d);
          },
          error: AjaxFailed
      });  
  </code></pre>
  
  <p>Server-side logic:</p>
  
  <pre><code>[WebMethod]
      public static string GetHexString(string strGetParamsString)
      {
          return "HI";
      }
  </code></pre>
  
  <p>Firebug shows 200 OK status. And the result is {"d":"HI"}
  <a href="http://jsonlint.com/" rel="nofollow">http://jsonlint.com/</a> says that json is valid.</p>
  
  <p>What is wrong?</p>