How can i create a popup(alert) message when a user enters a correct value or an incorrect value by clicking on the "Go" button . i am not sure how to connect the "Go" button with the java code .
please help
<%@ page import="java.io.*,java.util.*" %>
<html>
 <body>
<% 
 int a =6;
 int b = 8; 
%>
<FORM METHOD=POST ACTION="main.jsp">
 <%=a%>+<%=b%> =  <INPUT TYPE=TEXT NAME=num SIZE=20>
 <P><INPUT TYPE=SUBMIT value="Go"></p>
 <P><INPUT TYPE=SUBMIT value="Continue" disabled="disabled" ></p>
 </body>
 </html>
 
    