Parse error: syntax error, unexpected $end in mydirectory\index.php on line 21

I am getting this message, and do not know why. does anybody know why? (line 21 is the last line of code)
Hope you can help, Thanks!
Here is my index.php code:

<?php get_header(); ?>

    <?php get_sidebar(); ?>

      <div class="main-content">
      <?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>
<!-- WordPress loop here -->
        <div class="column1-unit">
          <h1><a href="<?php the_permalink() ?>" rel="bookmark" title='Click to read: "<?php strip_tags(the_title()); ?>"'><?php the_title(); ?></a></h1>
          <h3><?php the_date(); ?>, by <?php the_author(); ?></h3>
          <p><?php the_content("Continue reading '" . the_title('', '', false) . "'"); ?></p>
          <p class="details">| Posted by <?php the_author(); ?> | Categories: <?php the_category(', '); ?> | Comments: <?php comments_number('zero', 'one', 'more', 'number'); ?> |</p>
          <?php endwhile; ?>
          </div>
        <hr class="clear-contentunit" />

      </div>
    </div>
<?php get_footer(); ?>
</div>