diff -r 000000000000 -r 6474c204b198 browser/themes/windows/aboutPrivateBrowsing.css
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/themes/windows/aboutPrivateBrowsing.css	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,47 @@
+%if 0
+/* 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/. */
+%endif
+
+body.private > #errorPageContainer {
+  background-image: url("chrome://browser/skin/Privacy-48.png");
+}
+
+body.normal > #errorPageContainer {
+  background-image: url("chrome://global/skin/icons/question-48.png");
+}
+
+#clearRecentHistoryDesc {
+  margin-top: 2em;
+}
+
+#clearRecentHistoryDesc > p {
+  font-size: 110%; /* to match the value set in chrome://global/skin/netError.css */
+}
+
+#startPrivateBrowsingDesc > button {
+  -moz-margin-start: 0;
+}
+
+#footerDesc > p {
+  font-size: 110%; /* to match the value set in chrome://global/skin/netError.css */
+}
+
+#moreInfo {
+  font-size: 110%; /* to match the value set in chrome://global/skin/netError.css */
+  -moz-padding-start: 25px;
+  background: url("chrome://global/skin/icons/information-16.png") no-repeat top left;
+}
+
+#moreInfo:-moz-dir(rtl) {
+  background-position: top right;
+}
+
+#moreInfoText {
+  margin-bottom: 0;
+}
+
+#moreInfoLinkContainer {
+  margin-top: 0.5em;
+}