function getScrollTop() {

     var scrollPos;

     if (window.pageYOffset) {

     scrollPos = window.pageYOffset;

     }else if (document.compatMode && document.compatMode != 'BackCompat') {

             scrollPos = document.documentElement.scrollTop; }

     else if (document.body) {

             scrollPos = document.body.scrollTop;

         } return scrollPos;

 }