Validation

Validation using jquery

HTML

<script src="http://ajax.microsoft.com/ajax/jquery.validate/1.7/jquery.validate.min.js"></script>
<form>
  <input type='text' name='foo' id='foo' class='required' /> 
  <input type="submit" />
</form>

CSS

form > * {
  margin: 20px;
  display: block;
}

JavaScript

$("form").validate({
  focusInvalid: false,
  messages: {
    foo: {
      required: 'This field is required, <a href="#" onclick="alert(0);$(\'#foo\').focus(); return false;">click here to find out why</a>',
    }
  }
});