Get highest rated post

Hello,

i am a little new to php and WordPress ;(

i am trying to get the highest rated post on a page but it cant get it to work hope someone can help me out here is my code but i dont think that its good ?

<?php
			$args = array( 'numberposts' => -1, 'orderby' => 'desc', 'sortby' => 'highest_rated',  );
			$postslist = get_posts( $args );
			foreach ($postslist as $post) :  setup_postdata($post); ?>
			    <div>
			            <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
			              <br />
			            <?php the_date(); ?>
			            <br />
			          <?php the_excerpt(); ?>
			   </div>
			<?php endforeach; ?>

Greetings

http://wordpress.org/extend/plugins/wp-postratings/