//var viewportwidth;
 var viewportheight;
 // de standaard browsers (mozilla/netscape/opera/IE7) gebruiken window.innerWidth en window.innerHeight
  if (typeof window.innerWidth != 'undefined')
 {
 //     viewportwidth = window.innerWidth,
      viewportheight = window.innerHeight
 }
 // IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
 else if (typeof document.documentElement != 'undefined'
     && typeof document.documentElement.clientWidth !=
     'undefined' && document.documentElement.clientWidth != 0)
 {
 //      viewportwidth = document.documentElement.clientWidth,
       viewportheight = document.documentElement.clientHeight
 }
  // older versions of IE
 else
 {
 //      viewportwidth = document.getElementsByTagName('body')[0].clientWidth;
       viewportheight = document.getElementsByTagName('body')[0].clientHeight;
 }