function getWindowheight () {
         var viewportwidth ;
         var viewportheight ;
         switch (true)
		        {
                case typeof window.innerWidth !== 'undefined' :
// The more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
                   viewportwidth = window.innerWidth ;
                   viewportheight = window.innerHeight ;
                   break ;
		case (typeof document.documentElement !== 'undefined') && (typeof document.documentElement.clientWidth !== 'undefined') && (document.documentElement.clientWidth !== 0) :
// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
                   viewportwidth = document.documentElement.clientWidth ;
                   viewportheight = document.documentElement.clientHeight ;
                   break ;
                default :
// Older versions of IE
                   viewportwidth = document.getElementsByTagName('body')[0].clientWidth ;
                   viewportheight = document.getElementsByTagName('body')[0].clientHeight ;
                } ;
         return viewportheight ;
         } ;