Index: wp-content/themes/twentyeleven/style.css
===================================================================
--- wp-content/themes/twentyeleven/style.css	(revision 18059)
+++ wp-content/themes/twentyeleven/style.css	(working copy)
@@ -710,6 +710,11 @@
 .entry-meta a {
 	font-weight: bold;
 }
+.single-author .entry-meta .by-author {
+	position: absolute !important;
+	clip: rect(1px 1px 1px 1px); /* IE6, IE7 */
+	clip: rect(1px, 1px, 1px, 1px);
+}
 .entry-content,
 .entry-summary {
 	padding: 1.625em 0 0;
Index: wp-content/themes/twentyeleven/functions.php
===================================================================
--- wp-content/themes/twentyeleven/functions.php	(revision 18059)
+++ wp-content/themes/twentyeleven/functions.php	(working copy)
@@ -558,4 +558,38 @@
 			break;
 	endswitch;
 }
-endif; // ends check for twentyeleven_comment()
\ No newline at end of file
+endif; // ends check for twentyeleven_comment()
+
+if ( ! function_exists( 'twentyeleven_posted_on' ) ) :
+/**
+ * Prints HTML with meta information for the current post-date/time and author.
+ *
+ * @since Twenty Eleven 1.0
+ */
+function twentyeleven_posted_on() {
+	printf( __( '<span class="sep">Posted on </span><a href="%1$s" title="%2$s" rel="bookmark"><time class="entry-date" datetime="%3$s" pubdate>%4$s</time></a><span class="by-author"> <span class="sep"> by </span> <span class="author vcard"><a class="url fn n" href="%5$s" title="%6$s">%7$s</a></span></span>', 'twentyeleven' ),
+		esc_url( get_permalink() ),
+		esc_attr( get_the_time() ),
+		esc_attr( get_the_date( 'c' ) ),
+		esc_html( get_the_date() ),
+		esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
+		sprintf( esc_attr__( 'View all posts by %s', 'twentyeleven' ), get_the_author() ),
+		esc_html( get_the_author() )
+	);
+}
+endif;
+
+/**
+ * Adds Twenty Eleven author class to the array of body classes.
+ *
+ * @since Twenty Eleven 1.0
+ */
+function twentyeleven_author_class( $classes ) {
+
+	if ( ! is_multi_author() ) {
+		$classes[] = 'single-author';
+	}
+	
+	return $classes;
+}
+add_filter( 'body_class', 'twentyeleven_author_class' );