Server side code could not access from javascript - reg

ShowTable = function()
{
    var Obj= $get('pid').value;
    PageMethods.GivemeContent(Obj,OnSuccess)
    alert(Obj);

}
OnSuccess= function(result)
{
  var Obj= $get('mydiv');
  Obj.innerHTML=result;
}

[System.Web.Services.WebMethod]
    [System.Web.Script.Services.ScriptMethod]

       public static string GivemeContent(string value)
    {
        return @"DemoString";
    }

<ajax:ScriptManager ID="ScriptManager1" runat="server"
       EnablePageMethods="true" EnablePartialRendering="true">
            </ajax:ScriptManager>
       <ajax:UpdatePanel ID="myupdatePanel" runat="server" UpdateMode="Conditional">
       <ContentTemplate>
       <div>
       Your Name :
       <asp:TextBox ID="pid" runat="server" ></asp:TextBox>
       <input id="btn" type="button" value="Show Table" onclick="ShowTable()"/>
       </div>
       <div id="mydiv" runat="server">
         </div>
       </ContentTemplate>
       </ajax:UpdatePanel>