Index: wp-admin/widgets.php
===================================================================
--- wp-admin/widgets.php	(revision 18510)
+++ wp-admin/widgets.php	(working copy)
@@ -390,7 +390,7 @@
 	if ( 'wp_inactive_widgets' == $sidebar )
 		continue;
 	$closed = $i ? ' closed' : ''; ?>
-	<div class="widgets-holder-wrap<?php echo $closed; ?>">
+	<div class="widgets-holder-wrap<?php echo $closed; ?>" id="<?php echo esc_attr($sidebar) . '-holder-wrap' ?>">
 	<div class="sidebar-name">
 	<div class="sidebar-name-arrow"><br /></div>
 	<h3><?php echo esc_html( $registered_sidebar['name'] ); ?>