css3 - how to make fluid height via bootstrap or @media-query? -

i use bootstrap fluid grid system.

i have div class .span6 , set heigth:200px this.

now want when window re-sizing div's height decrease width.

http://jsfiddle.net/prince4prodigy/x8zu8/

<div class="container-fluid">     <div class="row-fluid">          <div class="span6"></div>          <div class="span3"></div>          <div class="span3"></div>      </div> </div> 

that depends in divs , how site designed...

if want decrease size have make via js, or start positioning elements absolute.

if site designed 100% height of window, can make elements absolute , easy.

but if site isn't 100% of window height, solution via javscript.