title: div position relative to parent height
body: <p>I have a '#Index-BG' with 80% of window.innerHeight. Now I need this child '#Verticais-R' which is rotated CW 90º to be vertical align center relatively to the 80% of parent's height.</p>
  
  <p>Here's what I'm trying to do:</p>
  
  <pre><code>var div=document.getElementById('Verticais-R'); 
  div.setAttribute('style', '-ms-transform-origin: center center; position:absolute; top:'+ (document.getElementById('Index-BG').style.clientHeight-500) *0.5+'px; right:+35px;') ;
  </code></pre>
  
  <p>any tips? I think the problem here is that it's not recognising parent's height?</p>