function watchFields( form ) {
      // Go through all the field elements in form
      for ( var i = 0; i < form.elements.length; i++ ) {
  
          // and attach a 'blur' event handler (which watches for a user
          // to lose focus of an input element)
          addEvent( form.elements[i], 'blur',  function(){
             // Once the focus has been lost, re-validate the field
             return validateField( this );
          });
  
      }
  }
  
  // Locate the first form on the page
  var form = document.getElementsByTagName( "form" )[0];
  
  // Watch all the fields in the form for changes
  watchFields( form );