title: jQuery Add Transparent Overlay on Menu Hover
body: <p>I am trying to recreate the effect found <a href="http://www.johnlewis.com/" rel="nofollow">here</a></p>
  
  <p>When hovering over the mega menu li > a element the background / opacity changes over the page wrapper I am assuming but I am not sure the best way to achieve this with jQuery.</p>
  
  <p>Should I use css to change the background or opacity or jQuery itself to try to recreate this effect. </p>
  
  <p>Any pointers would be much appreciated.</p>