diff --git a/wp-admin/admin-header.php b/wp-admin/admin-header.php
index 319b6ecf52..2d6b33177f 100644
--- a/wp-admin/admin-header.php
+++ b/wp-admin/admin-header.php
@@ -15,8 +15,7 @@ wp_user_settings();
 wp_menu_unfold();
 ?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-<html xmlns="http://www.w3.org/1999/xhtml" <?php do_action('admin_xml_ns'); ?> <?php language_attributes();
-echo strpos($_SERVER['HTTP_USER_AGENT'], 'Firefox/3.5') !== false ? ' manifest="cache-manifest.php"' : ''; ?>>
+<html xmlns="http://www.w3.org/1999/xhtml" <?php do_action('admin_xml_ns'); ?> <?php language_attributes(); ?>>
 <head>
 <meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php echo get_option('blog_charset'); ?>" />
 <title><?php echo $title; ?> &lsaquo; <?php bloginfo('name') ?>  &#8212; WordPress</title>
