javascript message on web app

In a vb.net 2010 web form application, I have the following code:
<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="default.aspx.vb" Inherits="attendanceletters_default" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>

   
       
    <%If (False) Then%>
       
    <% End If%>   
   
   
        function GetStudentLetterTemplate(schoolyear, schoolnum, milestone, studentlink, language, semester) {

            alert('schoolyear: ' + schoolyear + 'schoolnum: ' + schoolnum + 'milestone: ' + milestone + 'studentlink: ' + studentlink + 'language: ' + language + 'semester: ' + semester);
             if (milestone == '999') {
                 alert('You have selected student(s) having more than one CAIP entry for the current school year');
               return;
            }
}

I want to display a javascript alert message in production when an error condition exists. The code listed above works in a development envirnonment,
but the code would not deploy to a test app server.

Thus can you show me what I can do to fix the code listed above?

 If not, would you show me what I can do in a production environment to have a warning message displayed to a user with the least amount of extra code?
 I do not care how the warning message is displayed, I just want a warning message to be displayed.