Index: src/wp-admin/css/colors/_admin.scss
===================================================================
--- src/wp-admin/css/colors/_admin.scss	(revision 29025)
+++ src/wp-admin/css/colors/_admin.scss	(working copy)
@@ -453,6 +453,16 @@
 	color: $menu-highlight-text;
 }
 
+.theme-install-overlay .close-full-overlay:hover,
+.theme-install-overlay .close-full-overlay:focus,
+.theme-install-overlay .previous-theme:hover,
+.theme-install-overlay .previous-theme:focus,
+.theme-install-overlay .next-theme:hover,
+.theme-install-overlay .next-theme:focus {
+	background-color: $menu-highlight-background;
+	color: $menu-highlight-text;
+}
+
 /* Widgets */
 
 .widgets-chooser li.widgets-chooser-selected {
@@ -472,6 +482,8 @@
 	color: $menu-highlight-text;
 }
 
+.customize-controls-close:focus,
+.customize-controls-close:hover,
 .control-panel-back:focus,
 .control-panel-back:hover {
 	background-color: $menu-highlight-background;
Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 29025)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -170,6 +170,22 @@
 	width: 100%;
 }
 
+.customize-controls-close {
+	display: block;
+	position: absolute;
+	top: 0;
+	left: 0;
+	width: 45px;
+	height: 45px;
+	padding-right: 2px;
+	background: #eee;
+	border-right: 1px solid #ddd;
+	color: #444;
+	cursor: pointer;
+	-webkit-transition: color ease-in .1s;
+	transition: color ease-in .1s;
+}
+
 .control-panel-back {
 	display: block;
 	position: fixed;
@@ -190,13 +206,25 @@
 	display: none;
 }
 
+.customize-controls-close:focus,
+.customize-controls-close:hover,
 .control-panel-back:focus,
 .control-panel-back:hover {
 	background-color: #0074a2;
 	color: #fff;
 	outline: none;
+	-webkit-box-shadow: none;
+	box-shadow: none;
 }
 
+.customize-controls-close:before {
+	font: normal 32px/1 dashicons;
+	content: "\f335";
+	position: relative;
+	top: 8px;
+	left: 8px;
+}
+
 .control-panel-back:before {
 	font: normal 29px/1 dashicons;
 	content: "\f340";
@@ -217,17 +245,6 @@
 	height: 22px;
 }
 
-#customize-header-actions a.back {
-	position: relative;
-	left: 0;
-	-webkit-transition: left ease-in-out .18s;
-	transition: left ease-in-out .18s;
-}
-
-.in-sub-panel #customize-header-actions a.back {
-	left: -120px;
-}
-
 .wp-full-overlay-sidebar .wp-full-overlay-header {
 	-webkit-transition: padding ease-in-out .18s;
 	transition: padding ease-in-out .18s;
Index: src/wp-admin/css/themes.css
===================================================================
--- src/wp-admin/css/themes.css	(revision 29025)
+++ src/wp-admin/css/themes.css	(working copy)
@@ -1617,11 +1617,85 @@
 	overflow: auto;
 }
 
-/* Close Link */
-.wp-full-overlay .close-full-overlay {
+/* Close & Navigation Links */
+.theme-install-overlay .wp-full-overlay-sidebar .wp-full-overlay-header {
+	padding: 0;
+}
+
+.theme-install-overlay .close-full-overlay,
+.theme-install-overlay .previous-theme,
+.theme-install-overlay .next-theme {
+	display: block;
+	position: relative;
+	float: left;
+	width: 45px;
+	height: 45px;
+	padding-right: 2px;
+	background: #eee;
+	border-right: 1px solid #ddd;
+	color: #444;
+	cursor: pointer;
 	text-decoration: none;
+	-webkit-transition: color ease-in .1s;
+	transition: color ease-in .1s;
 }
 
+.theme-install-overlay .close-full-overlay:hover,
+.theme-install-overlay .close-full-overlay:focus,
+.theme-install-overlay .previous-theme:hover,
+.theme-install-overlay .previous-theme:focus,
+.theme-install-overlay .next-theme:hover,
+.theme-install-overlay .next-theme:focus {
+	background-color: #0074a2;
+	color: #fff;
+	outline: none;
+	-webkit-box-shadow: none;
+	box-shadow: none;
+}
+
+.theme-install-overlay .close-full-overlay:before {
+	font: normal 30px/1 dashicons;
+	content: "\f335";
+	position: relative;
+	top: 9px;
+	left: 9px;
+}
+
+.theme-install-overlay .previous-theme:before {
+	font: normal 20px/1 dashicons;
+	content: "\f340";
+	position: relative;
+	top: 6px;
+	left: 14px;
+}
+
+.theme-install-overlay .next-theme:before {
+	font: normal 20px/1 dashicons;
+	content: "\f344";
+	position: relative;
+	top: 6px;
+	left: 13px;
+}
+
+.theme-install-overlay .previous-theme.disabled,
+.theme-install-overlay .next-theme.disabled,
+.theme-install-overlay .previous-theme.disabled:hover,
+.theme-install-overlay .previous-theme.disabled:focus,
+.theme-install-overlay .next-theme.disabled:hover,
+.theme-install-overlay .next-theme.disabled:focus {
+	color: #bbb;
+	background: #eee;
+	cursor: default;
+}
+
+.rtl .theme-install-overlay .previous-theme:before {
+	content: "\f344";
+}
+
+.rtl .theme-install-overlay .next-theme:before {
+	content: "\f340";
+}
+
 /* Collapse Button */
 .wp-full-overlay a.collapse-sidebar {
 	position: absolute;
@@ -1704,19 +1778,6 @@
 	display: none;
 }
 
-.wp-full-overlay .theme-navigation {
-	padding: 10px 20px;
-	position: absolute;
-		bottom: 10px;
-	text-align: left;
-}
-.wp-full-overlay .theme-navigation .next-theme {
-	float: right;
-}
-.wp-full-overlay.no-navigation .theme-navigation {
-	display: none;
-}
-
 /* Animations */
 .wp-full-overlay,
 .wp-full-overlay-sidebar,
@@ -1845,21 +1906,24 @@
 	max-width: 100%;
 }
 
-.theme-install-overlay .wp-full-overlay-header {
-	margin-top: 9px;
-}
-
 .theme-install-overlay .wp-full-overlay-header .theme-install {
 	float: right;
+	margin: 8px 10px 0 0;
 	/* For when .theme-install is a span rather than a.button-primary (already installed theme) */
 	line-height: 26px;
 }
 
 .theme-install-overlay .wp-full-overlay-sidebar {
-	background: #EEE;
-	border-right: 1px solid #DDD;
+	background: #eee;
+	border-right: 1px solid #ddd;
 }
 
+.theme-install-overlay .wp-full-overlay-sidebar-content {
+	background: #fff;
+	border-top: 1px solid #ddd;
+	border-bottom: 1px solid #ddd;
+}
+
 .theme-install-overlay .wp-full-overlay-main {
 	background: #fff url(../images/spinner.gif) no-repeat center center;
 	-webkit-background-size: 20px 20px;
Index: src/wp-admin/customize.php
===================================================================
--- src/wp-admin/customize.php	(revision 29025)
+++ src/wp-admin/customize.php	(working copy)
@@ -108,8 +108,8 @@
 				submit_button( $save_text, 'primary save', 'save', false );
 			?>
 			<span class="spinner"></span>
-			<a class="back button" href="<?php echo esc_url( $return ? $return : admin_url( 'themes.php' ) ); ?>">
-				<?php _e( 'Cancel' ); ?>
+			<a class="customize-controls-close" href="<?php echo esc_url( $return ? $return : admin_url( 'themes.php' ) ); ?>">
+				<span class="screen-reader-text"><?php _e( 'Cancel' ); ?></span>
 			</a>
 		</div>
 
Index: src/wp-admin/js/customize-controls.js
===================================================================
--- src/wp-admin/js/customize-controls.js	(revision 29025)
+++ src/wp-admin/js/customize-controls.js	(working copy)
@@ -916,7 +916,7 @@
 		var previewer, parent, topFocus,
 			body = $( document.body ),
 			overlay = body.children( '.wp-full-overlay' ),
-			backBtn = $( '.back' ),
+			closeBtn = $( '.customize-controls-close' ),
 			saveBtn = $( '#save' );
 
 		// Prevent the form from saving when enter is pressed on an input or select element.
@@ -1044,15 +1044,15 @@
 			state.bind( 'change', function() {
 				if ( ! activated() ) {
 					saveBtn.val( api.l10n.activate ).prop( 'disabled', false );
-					backBtn.text( api.l10n.cancel );
+					closeBtn.find( '.screen-reader-text' ).text( api.l10n.cancel );
 
 				} else if ( saved() ) {
 					saveBtn.val( api.l10n.saved ).prop( 'disabled', true );
-					backBtn.text( api.l10n.close );
+					closeBtn.find( '.screen-reader-text' ).text( api.l10n.close );
 
 				} else {
 					saveBtn.val( api.l10n.save ).prop( 'disabled', false );
-					backBtn.text( api.l10n.cancel );
+					closeBtn.find( '.screen-reader-text' ).text( api.l10n.cancel );
 				}
 			});
 
@@ -1091,7 +1091,7 @@
 			event.preventDefault();
 		});
 
-		backBtn.keydown( function( event ) {
+		closeBtn.keydown( function( event ) {
 			if ( 9 === event.which ) // tab
 				return;
 			if ( 13 === event.which ) // enter
@@ -1121,7 +1121,7 @@
 		// If we receive a 'back' event, we're inside an iframe.
 		// Send any clicks to the 'Return' link to the parent page.
 		parent.bind( 'back', function() {
-			backBtn.on( 'click.back', function( event ) {
+			closeBtn.on( 'click.customize-controls-close', function( event ) {
 				event.preventDefault();
 				parent.send( 'close' );
 			});
@@ -1206,7 +1206,7 @@
 		api.trigger( 'ready' );
 
 		// Make sure left column gets focus
-		topFocus = backBtn;
+		topFocus = closeBtn;
 		topFocus.focus();
 		setTimeout(function () {
 			topFocus.focus();
Index: src/wp-admin/theme-install.php
===================================================================
--- src/wp-admin/theme-install.php	(revision 29025)
+++ src/wp-admin/theme-install.php	(working copy)
@@ -225,7 +225,9 @@
 <script id="tmpl-theme-preview" type="text/template">
 	<div class="wp-full-overlay-sidebar">
 		<div class="wp-full-overlay-header">
-			<a href="#" class="close-full-overlay button-secondary"><?php _e( 'Close' ); ?></a>
+			<a href="#" class="close-full-overlay"><span class="screen-reader-text"><?php _e( 'Close' ); ?></span></a>
+			<a href="#" class="previous-theme"><span class="screen-reader-text"><?php _ex( 'Previous', 'Button label for a theme' ); ?></span></a>
+			<a href="#" class="next-theme"><span class="screen-reader-text"><?php _ex( 'Next', 'Button label for a theme' ); ?></span></a>
 		<# if ( data.installed ) { #>
 			<a href="#" class="button button-primary theme-install disabled"><?php _ex( 'Installed', 'theme' ); ?></a>
 		<# } else { #>
@@ -262,10 +264,6 @@
 				<span class="collapse-sidebar-label"><?php _e( 'Collapse' ); ?></span>
 				<span class="collapse-sidebar-arrow"></span>
 			</a>
-			<div class="theme-navigation">
-				<a class="previous-theme button" href="#"><?php _ex( 'Previous', 'Button label for a theme' ); ?></a>
-				<a class="next-theme button" href="#"><?php _ex( 'Next', 'Button label for a theme' ); ?></a>
-			</div>
 		</div>
 	</div>
 	<div class="wp-full-overlay-main">