diff -r 000000000000 -r 6474c204b198 toolkit/components/alerts/resources/content/alert.css
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/alerts/resources/content/alert.css	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#alertBox[animate] {
+  animation-duration: 4s;
+  animation-fill-mode: both;
+  animation-name: alert-animation;
+}
+
+#alertBox[animate]:hover {
+  animation-play-state: paused;
+}
+
+.alertText {
+  white-space: pre-wrap;
+}
+
+@keyframes alert-animation {
+  to {
+    visibility: hidden;
+  }
+}