Better footnote popup positioning

lib/scripts/script.js

@@ -263,7 +263,7 @@ function insitu_popup(target, popup_id) {
     // position the div and make it visible
     fndiv.style.position = 'absolute';
     fndiv.style.left = findPosX(target)+'px';
-    fndiv.style.top  = (findPosY(target)+target.scrollHeight * 1.5) + 'px';
+    fndiv.style.top  = (findPosY(target)+target.offsetHeight * 1.5) + 'px';
     fndiv.style.display = '';
     return fndiv;
 }