Startup Design Framework - How to implement Parallax

gistfile1.js

// Parallax - paste this code in script.js

$('.content-23.custom-bg').each(function() {
  if(! isMobile.any())
   $(this).parallax('50%', 0.3, true);
  else
   $(this).css('background-attachment', 'initial');
}); 

gistfile2.css

/* paste this code in style.css */

.content-23.custom-bg {
  background-image: url('../../path/to/image.jpg');
  background-position: 50% 50%;
  background-repeat: no-repeat;
  background-attachment: fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  background-size: cover;
}

gistfile3.html

<!-- Place in this order at the end of the document so the pages load faster -->
<script src="../../common-files/js/jquery.parallax.min.js"></script>
<script src="../../js/script.js"></script>