Error in inserting data with JSON and Ajax

Error in inserting data with JSON and Ajax

i don't know where is Problem, code looks fine and i tried hard but
getting Error aLL the time
please any one help me
this is my code
my lib.
<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>
and my JSON CODE :-
<script type="text/javascript">
$(document).ready(function(){
$("#Button1").click(function(){
var Name=document.getElementById('Text1').value
var Class=document.getElementById('Text2').value
var Data=JSON.stringify({Name:Name,Class:Class});
alert(Data);
$.ajax({
type: 'POST',
contentType: "application/json; charset=utf-8",
url: 'Default.aspx/InsertData',
data:Data,
async: false,
success: function (response) {
$('#Text1').val('');
$('#Text2').val('');
},
error: function ()
{ alert("Error") }
});
});
});
</script>
and function is
[WebMethod]
public string InsertData(string Name, string Class)
{
SqlCommand cmd = new SqlCommand("Insert into
employee(EmployeeName,Class) values(@EmpName,@Classs)",con);
cmd.Parameters.AddWithValue("@EmpName", Name);
cmd.Parameters.AddWithValue("@Classs",Class);
cmd.ExecuteNonQuery();
con.Close();
return "True";
}
enter code here