For full explanation see here http://shaunhare.co.uk/formalarkey/

Optional Fields jQuery Plugin

A jQuery plugin as requested by Andy Clarke (http://stuffandnonsense.co.uk, @Malarkey) to have effect as described in Andy Clarke's original blog post

Example usage

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script> <script src="jquery.toggleOptionalFields.js" type="text/javascript"></script>

<script>
    $(document).ready(function()
        {
              $("#example-form").toggleOptionalFields();
                  });
</script>