Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 23695)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -2202,6 +2202,9 @@
 	width: 100%;
 }
 
+.error404 .page-content #s {
+	width: 100%;
+}
 
 /**
  * 5.12 Comments