// JavaScript Document
<script language="JavaScript">
<!-- Picks a random image number
var number_of_images = 6
var image_number = Math.floor((number_of_images*0.999*Math.random())+1);
// -->

function validateOnSubmit(){
if (isNaN(document.forms[0].ZipCode.value))
{
    alert("Please enter a number for the Zip Code.");
    document.forms[0].ZipCode.focus();
   return (false);
  }
if (""==document.forms[0].ZipCode.value.charAt(4))
{
    alert("Please enter a 5 digit zip code.");
    document.forms[0].ZipCode.focus();
   return (false);
  }
document.forms[0].action = document.forms[0].action + document.forms[0].ZipCode.value;
return (true);
}
</script>