<form id="demo-form" data-parsley-validate>
  <div class="first block1 show">
    <label for="firstname">Firstname:</label>
    <input type="text" name="firstname" data-parsley-group="block1" required/>

    <label for="lastname">Lastname:</label>
    <input type="text" name="lastname" data-parsley-group="block1" required />
    <span class="next btn btn-info pull-right" data-current-block="1" data-next-block="2">Next ></span>
  </div>

  <div class="second block2 hidden">
    <label for="fullname">Email:</label>
    <input type="text" name="fullname" required  data-parsley-type="email" data-parsley-group="block2" />
    <span class="next btn btn-info pull-left" data-current-block="2" data-next-block="1">< Previous</span>
    <input type="submit" class="btn btn-default pull-right" />
  </div>
</form>

<script type="text/javascript">
$(document).ready(function () {
  $('.next').on('click', function () {
    var current = $(this).data('currentBlock'),
      next = $(this).data('nextBlock');

    // only validate going forward. If current group is invalid, do not go further
    // .parsley().validate() returns validation result AND show errors
    if (next > current)
      if (false === $('#demo-form').parsley().validate('block' + current))
        return;

    // validation was ok. We can go on next step.
    $('.block' + current)
      .removeClass('show')
      .addClass('hidden');

    $('.block' + next)
      .removeClass('hidden')
      .addClass('show');

  });
});
</script>