Index: wp-admin/customize.php
===================================================================
--- wp-admin/customize.php	(revision 20951)
+++ wp-admin/customize.php	(working copy)
@@ -68,6 +68,7 @@
 		<div class="wp-full-overlay-sidebar-content">
 			<div id="customize-info" class="customize-section<?php if ( $cannot_expand ) echo ' cannot-expand'; ?>">
 				<div class="customize-section-title">
+				    /* translators: followed by the name of the theme */
 					<span class="preview-notice"><?php _e('You are previewing'); ?></span>
 					<strong class="theme-name"><?php echo $wp_customize->theme()->display('Name'); ?></strong>
 				</div>