function focus_zipcode() {
document.getElementById('zip').focus();
}

function check() {
  var RegExp = /^\d{5}([\-]\d{4})?$/;
   zip = document.getElementById('zip').value;
   if (!RegExp.test(zip)) {
        document.getElementById('zip').style.border='thin solid #9B0033';
        return false;
   }
}