Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21465)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -453,6 +453,12 @@
 /* Page structure */
 .wrapper {
 	overflow: hidden;
+	-moz-hyphens: auto;
+	-ms-word-break: break-all;
+	-webkit-hyphens: auto;
+	hyphens: auto;
+	word-break: break-all;
+	word-break: break-word;
 }
 .site {
 	padding: 0 24px;