Index: wp-content/themes/twentythirteen/functions.php
===================================================================
--- wp-content/themes/twentythirteen/functions.php	(revision 23494)
+++ wp-content/themes/twentythirteen/functions.php	(working copy)
@@ -544,6 +544,25 @@
 add_filter( 'the_content', 'twentythirteen_aside_date', 8 ); // After embeds, before everything else.
 
 /**
+ * Add anchor hash to image attachment links.
+ *
+ * Appends a hash anchor to attachment link URLs, which moves the focus down to
+ * the main content area to view the image when the attachment page loads.
+ *
+ * @since Twenty Thirteen 1.0
+ *
+ * @param string $url The image attachment URL
+ * @return string
+ */
+function twentythirteen_attachment_link( $url ) {
+	if ( wp_attachment_is_image() )
+		$url .= '#main';
+
+	return $url;
+}
+add_filter( 'attachment_link', 'twentythirteen_attachment_link' );
+
+/**
  * Add postMessage support for site title and description for the Customizer.
  *
  * @since Twenty Thirteen 1.0