Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21405)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -838,9 +838,12 @@
 	margin-bottom: 12px;
 	margin-bottom: 0.857142857rem;
 }
-.entry-content iframe {
+.entry-content embed,
+.entry-content iframe,
+.entry-content object {
 	margin-bottom: 24px;
 	margin-bottom: 1.714285714rem;
+	max-width: 100%;
 }
 .entry-content dl,
 .comment-content dl {