Index: wp-admin/css/edit.css
===================================================================
--- wp-admin/css/edit.css	(revision 41614)
+++ wp-admin/css/edit.css	(working copy)
@@ -214,7 +214,7 @@
 
 /* Back-compat for pre-4.4 */
 #category-adder h4 {
-    margin: 0;
+	margin: 0;
 }
 
 .taxonomy-add-new {
@@ -498,18 +498,38 @@
 	border-style: solid;
 }
 
+.notification-dialog-wrap {
+	position: fixed;
+	z-index: 10000;
+	top: 0;
+	right: 0;
+	bottom: 0;
+	left: 0;
+	overflow: auto;
+	text-align: center;
+	-webkit-backface-visibility: hidden;
+	backface-visibility: hidden;
+}
+
+.notification-dialog-wrap::before {
+	content: '';
+	display: inline-block;
+	height: 100%;
+	vertical-align: middle;
+}
+
 .notification-dialog {
-	position: fixed;
-	top: 30%;
-	max-height: 70%;
-	left: 50%;
-	width: 450px;
-	margin-left: -225px;
+	display: inline-block;
+	position: relative;
+	max-width: 450px;
+	width: 100%;
 	background: #fff;
 	box-shadow: 0 3px 6px rgba( 0, 0, 0, 0.3 );
 	line-height: 1.5;
 	z-index: 1000005;
 	overflow-y: auto;
+	vertical-align: middle;
+	text-align: left;
 }
 
 .notification-dialog-background {