--- a/suite/themes/modern/global/global.css
+++ b/suite/themes/modern/global/global.css
@@ -185,16 +185,17 @@ description.error {
   height: 28px;
   width: 28px;
   border: none;
   margin: -14px;
   padding: 0;
   background-image: url("chrome://global/skin/icons/autoscroll.png");
   background-color: transparent;
   -moz-appearance: none;
+  -moz-window-shadow: none;
 }
 
 #autoscroller[scrolldir="NS"] {
   background-position: left center;
 }
 
 #autoscroller[scrolldir="EW"] {
   background-position: left bottom;