Index: wp-content/themes/twentythirteen/functions.php
===================================================================
--- wp-content/themes/twentythirteen/functions.php	(revision 23480)
+++ wp-content/themes/twentythirteen/functions.php	(working copy)
@@ -572,3 +572,16 @@
  * Adds support for a custom header image.
  */
 require( get_template_directory() . '/inc/custom-header.php' );
+
+/**
+ * Add Anchor Hash to Attachment Page Navigation
+ *
+ * Appends a hash anchor to attachment link URLs, which jumps the page 
+ * focus down to view the attachment when the attachment page loads.
+ *
+ * @since Twenty Thirteen 1.0
+ */
+function twentythirteen_filter_attachment_url( $link ) {
+	return $link . '#main';
+}
+add_filter( 'attachment_link', 'twentythirteen_filter_attachment_url' );