function getViewportSize()
{
 var size = [0, 0];

 if (typeof window.innerWidth != 'undefined')
 {
   size = [
       window.innerWidth,
       window.innerHeight
   ];
 }
 else if (typeof document.documentElement != 'undefined'
     && typeof document.documentElement.clientWidth !=
     'undefined' && document.documentElement.clientWidth != 0)
 {
   size = [
       document.documentElement.clientWidth,
       document.documentElement.clientHeight
   ];
 }
 else
 {
   size = [
       document.getElementsByTagName('body')[0].clientWidth,
       document.getElementsByTagName('body')[0].clientHeight
   ];
 }

 return size;
}