function  getScrollTop(){ 
   // get the scroll distance from the top 
   var scrollTop; 
   if (typeof document.compatMode != 'undefined' && document.compatMode != 'BackCompat'){ 
     scrollTop = document.documentElement.scrollTop; 
   }else{ 
     scrollTop = document.body.scrollTop; 
   } 
   return (scrollTop); 
 }