I just attended a jQuery course, and the instructor demonstrated using Parsley ("the ultimate JavaScript form validation library"). I would like to use it my APEX form. It says installation is as follows:
<script src="jquery.js"></script>
<script src="parsley.min.js"></script>
<form id="form">
...
</form>
<script type="text/javascript">
$('#form').parsley();
</script