function getWindowSize() {
var w = window;
var d = w.document;
var e = d.documentElement;
var b = d.body;
var size = new Object();
size.width  = 0;
     size.height = 0;
   if( typeof( w.innerWidth ) == 'number' ) {
     size.width = w.innerWidth;
     size.height = w.innerHeight;
   } else if( e && ( e.clientWidth || e.clientHeight ) ) {
     size.width = e.clientWidth;
     size.height = e.clientHeight;
   } else if( b && ( b.clientWidth || b.clientHeight ) ) {
     size.width = b.clientWidth;
     size.height = b.clientHeight;
   }
return size;
}
  function vertAlign() {
var parent = document.getElementById('mainParent');
var content = document.getElementById('content');
var parentInfo = document.getElementById('parentInfo');
var contentInfo = document.getElementById('contentInfo');
var WinSize = getWindowSize() ;
if (WinSize.height > content.offsetHeight)
content.style.marginTop = (WinSize.height / 2) - 
(content.offsetHeight/2) +"px";
}