Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21474)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -1467,6 +1467,27 @@
 }
 
 
+/* =IE 8
+----------------------------------------------- */
+
+.ie .site { 
+	max-width: 960px; 
+	margin: 48px auto;
+}
+.ie .site-content { 
+	float: left;
+	width: 65.104166667%;
+}
+.ie .full-width .site-content {
+	float: none;
+	width: 100%;
+}
+.ie .widget-area { 
+	float: right;
+	width: 26.041666667%;
+}
+
+
 /* =Print
 ----------------------------------------------- */
 
Index: wp-content/themes/twentytwelve/header.php
===================================================================
--- wp-content/themes/twentytwelve/header.php	(revision 21474)
+++ wp-content/themes/twentytwelve/header.php	(working copy)
@@ -9,7 +9,12 @@
  * @since Twenty Twelve 1.0
  */
 ?><!DOCTYPE html>
+<!--[if IE 7 | IE 8]> 
+<html class="ie" <?php language_attributes(); ?>> 
+<![endif]--> 
+<!--[if !(IE 7) | !(IE 8)  ]><!--> 
 <html <?php language_attributes(); ?>>
+<!--<![endif]-->
 <head>
 <meta charset="<?php bloginfo( 'charset' ); ?>" />
 <meta name="viewport" content="width=device-width, initial-scale=1.0" />
