Code:
<html>
<head>
<script type="text/javascript" language="javascript">

function validate()
{
 if (document.form.fname.value=="")
 {
 alert("Enter your Name");
 document.form.fname.focus();
 return false;
 }

 if (document.form.age.value=="")
 {
 alert("Enter your Age");
 document.form.age.focus();
...