create special drop down menu

thanks to

http://wpguy.com/articles/an-archives-page-with-all-the-posts-in-cronological-order/

i got to this solution

<ul id="mainNav">
      <li><a href="">Archive</a>
      	<ul>
        <?php
		// Declare some helper vars
		$previous_year = $year = 0;
		$ul_open = false;
		// Get the posts
		$myposts = get_posts('numberposts=-1&orderby=post_date&order=DESC');
		foreach($myposts as $post) :
            // Setup the post variables
            setup_postdata($post);
            $year = mysql2date('Y', $post->post_date);
			if($year != $previous_year) :
				if($ul_open == true) : ?>
                    </ul></li>
                <?php endif; ?>
            <li><?php the_time('Y'); ?>
            <ul class="month_archive">
			<?php $ul_open = true;
			endif;
			$previous_year = $year;?>
                <li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
		<?php endforeach; ?>
        </ul></li></ul></li>

    </ul>