Index: src/wp-admin/about.php
===================================================================
--- src/wp-admin/about.php	(revision 36167)
+++ src/wp-admin/about.php	(working copy)
@@ -42,7 +42,7 @@
 		<div class="about-text"><?php printf( __( 'Thank you for updating! WordPress %s makes your site more connected and responsive.' ), $display_version ); ?></div>
 		<div class="wp-badge"><?php printf( __( 'Version %s' ), $display_version ); ?></div>
 
-		<h2 class="nav-tab-wrapper">
+		<h2 class="nav-tab-wrapper wp-clearfix">
 			<a href="about.php" class="nav-tab nav-tab-active"><?php _e( 'What&#8217;s New' ); ?></a>
 			<a href="credits.php" class="nav-tab"><?php _e( 'Credits' ); ?></a>
 			<a href="freedoms.php" class="nav-tab"><?php _e( 'Freedoms' ); ?></a>
Index: src/wp-admin/credits.php
===================================================================
--- src/wp-admin/credits.php	(revision 36167)
+++ src/wp-admin/credits.php	(working copy)
@@ -24,7 +24,7 @@
 
 <div class="wp-badge"><?php printf( __( 'Version %s' ), $display_version ); ?></div>
 
-<h2 class="nav-tab-wrapper">
+<h2 class="nav-tab-wrapper wp-clearfix">
 	<a href="about.php" class="nav-tab"><?php _e( 'What&#8217;s New' ); ?></a>
 	<a href="credits.php" class="nav-tab nav-tab-active"><?php _e( 'Credits' ); ?></a>
 	<a href="freedoms.php" class="nav-tab"><?php _e( 'Freedoms' ); ?></a>
Index: src/wp-admin/css/common.css
===================================================================
--- src/wp-admin/css/common.css	(revision 36167)
+++ src/wp-admin/css/common.css	(working copy)
@@ -114,6 +114,13 @@
 	clear: both;
 }
 
+/* modern clearfix */
+.wp-clearfix:after {
+	content: "";
+	display: table;
+	clear: both;
+}
+
 /* Hide visually but not from screen readers */
 .screen-reader-text,
 .screen-reader-text span,
@@ -2060,15 +2067,22 @@
 h3.nav-tab-wrapper {
 	border-bottom: 1px solid #ccc;
 	margin: 0;
-	padding: 9px 15px 0 0;
+	padding-top: 9px;
 	line-height: inherit;
 }
 
-/* contain floats */
-.nav-tab-wrapper:after {
-	content: "";
-	display: table;
-	clear: both;
+/* Back-compat for plugins. Deprecated. Use .wp-clearfix instead. */
+.nav-tab-wrapper:not(.wp-clearfix):after {
+ 	content: "";
+ 	display: table;
+ 	clear: both;
+ }
+
+.ie8 .nav-tab-wrapper {
+	/* contain floats establishing a new block formatting context */
+	display: inline-block;
+	width: 100%;
+	vertical-align: top;
 }
 
 /*------------------------------------------------------------------------------
@@ -3635,7 +3649,6 @@
 	h1.nav-tab-wrapper,
 	.wrap h2.nav-tab-wrapper,
 	h3.nav-tab-wrapper {
-		padding-left: 0;
 		border-bottom: 0;
 	}
 
@@ -3642,8 +3655,7 @@
 	h1 .nav-tab,
 	h2 .nav-tab,
 	h3 .nav-tab {
-		margin-top: 10px;
-		margin-right: 10px;
+		margin: 10px 10px 0 0;
 		border-bottom: 1px solid #ccc;
 	}
 }
Index: src/wp-admin/freedoms.php
===================================================================
--- src/wp-admin/freedoms.php	(revision 36167)
+++ src/wp-admin/freedoms.php	(working copy)
@@ -23,7 +23,7 @@
 
 <div class="wp-badge"><?php printf( __( 'Version %s' ), $display_version ); ?></div>
 
-<h2 class="nav-tab-wrapper">
+<h2 class="nav-tab-wrapper wp-clearfix">
 	<a href="about.php" class="nav-tab"><?php _e( 'What&#8217;s New' ); ?></a>
 	<a href="credits.php" class="nav-tab"><?php _e( 'Credits' ); ?></a>
 	<a href="freedoms.php" class="nav-tab nav-tab-active"><?php _e( 'Freedoms' ); ?></a>
Index: src/wp-admin/nav-menus.php
===================================================================
--- src/wp-admin/nav-menus.php	(revision 36167)
+++ src/wp-admin/nav-menus.php	(working copy)
@@ -584,7 +584,7 @@
 		endif;
 		?>
 	</h1>
-	<h2 class="nav-tab-wrapper">
+	<h2 class="nav-tab-wrapper wp-clearfix">
 		<a href="<?php echo admin_url( 'nav-menus.php' ); ?>" class="nav-tab<?php if ( ! isset( $_GET['action'] ) || isset( $_GET['action'] ) && 'locations' != $_GET['action'] ) echo ' nav-tab-active'; ?>"><?php esc_html_e( 'Edit Menus' ); ?></a>
 		<?php if ( $num_locations && $menu_count ) : ?>
 			<a href="<?php echo esc_url( add_query_arg( array( 'action' => 'locations' ), admin_url( 'nav-menus.php' ) ) ); ?>" class="nav-tab<?php if ( $locations_screen ) echo ' nav-tab-active'; ?>"><?php esc_html_e( 'Manage Locations' ); ?></a>
Index: src/wp-admin/network/site-info.php
===================================================================
--- src/wp-admin/network/site-info.php	(revision 36167)
+++ src/wp-admin/network/site-info.php	(working copy)
@@ -138,7 +138,7 @@
 <div class="wrap">
 <h1 id="edit-site"><?php echo $title; ?></h1>
 <p class="edit-site-actions"><a href="<?php echo esc_url( get_home_url( $id, '/' ) ); ?>"><?php _e( 'Visit' ); ?></a> | <a href="<?php echo esc_url( get_admin_url( $id ) ); ?>"><?php _e( 'Dashboard' ); ?></a></p>
-<h2 class="nav-tab-wrapper nav-tab-small">
+<h2 class="nav-tab-wrapper nav-tab-small wp-clearfix">
 <?php
 $tabs = array(
 	'site-info'     => array( 'label' => __( 'Info' ),     'url' => 'site-info.php'     ),
Index: src/wp-admin/network/site-settings.php
===================================================================
--- src/wp-admin/network/site-settings.php	(revision 36167)
+++ src/wp-admin/network/site-settings.php	(working copy)
@@ -95,7 +95,7 @@
 <div class="wrap">
 <h1 id="edit-site"><?php echo $title; ?></h1>
 <p class="edit-site-actions"><a href="<?php echo esc_url( get_home_url( $id, '/' ) ); ?>"><?php _e( 'Visit' ); ?></a> | <a href="<?php echo esc_url( get_admin_url( $id ) ); ?>"><?php _e( 'Dashboard' ); ?></a></p>
-<h2 class="nav-tab-wrapper nav-tab-small">
+<h2 class="nav-tab-wrapper nav-tab-small wp-clearfix">
 <?php
 $tabs = array(
 	'site-info'     => array( 'label' => __( 'Info' ),     'url' => 'site-info.php'     ),
Index: src/wp-admin/network/site-themes.php
===================================================================
--- src/wp-admin/network/site-themes.php	(revision 36167)
+++ src/wp-admin/network/site-themes.php	(working copy)
@@ -149,7 +149,7 @@
 <div class="wrap">
 <h1 id="edit-site"><?php echo $title; ?></h1>
 <p class="edit-site-actions"><a href="<?php echo esc_url( get_home_url( $id, '/' ) ); ?>"><?php _e( 'Visit' ); ?></a> | <a href="<?php echo esc_url( get_admin_url( $id ) ); ?>"><?php _e( 'Dashboard' ); ?></a></p>
-<h2 class="nav-tab-wrapper nav-tab-small">
+<h2 class="nav-tab-wrapper nav-tab-small wp-clearfix">
 <?php
 $tabs = array(
 	'site-info'     => array( 'label' => __( 'Info' ),     'url' => 'site-info.php'     ),
Index: src/wp-admin/network/site-users.php
===================================================================
--- src/wp-admin/network/site-users.php	(revision 36167)
+++ src/wp-admin/network/site-users.php	(working copy)
@@ -204,7 +204,7 @@
 <div class="wrap">
 <h1 id="edit-site"><?php echo $title; ?></h1>
 <p class="edit-site-actions"><a href="<?php echo esc_url( get_home_url( $id, '/' ) ); ?>"><?php _e( 'Visit' ); ?></a> | <a href="<?php echo esc_url( get_admin_url( $id ) ); ?>"><?php _e( 'Dashboard' ); ?></a></p>
-<h2 class="nav-tab-wrapper nav-tab-small">
+<h2 class="nav-tab-wrapper nav-tab-small wp-clearfix">
 <?php
 $tabs = array(
 	'site-info'     => array( 'label' => __( 'Info' ),     'url' => 'site-info.php'     ),