Index: wp-includes/class-wp-customize-manager.php
===================================================================
--- wp-includes/class-wp-customize-manager.php	(revision 20948)
+++ wp-includes/class-wp-customize-manager.php	(working copy)
@@ -280,7 +280,17 @@
 	 * @since 3.4.0
 	 */
 	public function customize_preview_base() {
-		?><base href="<?php echo home_url( '/' ); ?>" /><?php
+		?><base href="<?php echo home_url( '/' ); ?>" />
+		<!--[if lt IE 9]>
+		<script type="text/javascript">
+			var e = [ 'abbr', 'article', 'aside', 'audio', 'canvas', 'datalist', 'details',
+				'figure', 'footer', 'header', 'hgroup', 'mark', 'menu', 'meter', 'nav',
+				'output', 'progress', 'section', 'time', 'video' ];
+			for ( var i = 0; i < e.length; i++ ) {
+				document.createElement( e[i] );
+			}
+		</script>
+		<![endif]--><?php
 	}
 
 	/**