how to call WebMethod from asp.net page

[WebMethod]
    public static List<employee> FetchEmailList(string mail)
    {
       
        GM4LDataContext _this = new GM4LDataContext();
        List<employee> _AppUser = new List<employee>();
        var fetchEmail = _this.AppUsers.Where(m => m.FirstName.ToLower().StartsWith(mail.ToLower()));

        foreach (var item in fetchEmail)
        {
            _AppUser.Add(new Employee { Email = item.FirstName });
        }
        return _AppUser;
    }

<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/jquery-ui.min.js"></script>
<script type="text/javascript">
    $(function () {
        $(".tb").autocomplete({
            source: function (request, response) {
                $.ajax({
                    url: "Default.aspx/FetchEmailList",
                    data: "{ 'mail': '" + request.term + "' }",
                    dataType: "json",
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    dataFilter: function (data) { return data; },
                    success: function (data) {
                        response($.map(data.d, function (item) {
                            return {
                                value: item.Email
                            }
                        }))
                    },
                    error: function (XMLHttpRequest, textStatus, errorThrown) {
                        alert(textStatus);
                    }
                });
            },
            minLength: 2
        });
    });
</script>