I'm getting a Undefined value OnSuccess response and never fire a WebMethod.... (asp.Net vs2013, Framework 4.5 jquery 2.1.1)

This is MyCode:

2. <script>
3.         function fun() {
4.             PageMethods.GetPageMethod(onSucceed, onError);
5.             return false;
6.         }
7.         function onSucceed(result) {
8.             alert(result);              // HERE I Get a long HTML as Server Response instead a "Welcome PageMethods" string
9.         }                               // By the way, debugging never reach a breakpoint inside GetPageMethod 
10.         function onError(result) {
11.         }
12.     </script>