diff --git a/progros.css b/progros.css
index 7184474..c22ec5e 100644
--- a/progros.css
+++ b/progros.css
@@ -98,7 +98,8 @@ body {
   background-size: 100% 100%;
   -webkit-background-size: 100% 100%;
   -o-background-size: 100% 100%;
-  -moz-background-size: 100%, 100%;
+  -moz-background-size: 100% 100%;
+  background-attachment: fixed;
   text-align: center;
   margin-top: 1em;
 }