stacked posts grid

<?php $num_cols = 3; // set the number of columns here

if (have_posts()) :
for ( $i=1 ; $i <= $num_cols; $i++ ) :
echo '<div id="col-'.$i.'" class="col">';
$counter = $num_cols + 1 - $i;
while (have_posts()) : the_post();
if( $counter%$num_cols == 0 ) : ?>

<div class="postarray">
<a class="posttitle" title="<?php the_title(); ?>" href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a>
<p class="meta"> <?php the_time('jS F Y') ?>//<?php the_category(', ') ?>//<?php the_author(); ?></p>
<?php the_post_thumbnail(array(300,9999), array ('class' => 'alignleft')); ?>
<p class="thumbtext"><?php the_excerpt(); ?> </p>
<div class="clear"></div>
</div>

<?php endif; $counter++;
endwhile;
rewind_posts();
echo '</div>'; //closes the column div
endfor;

endif; ?>
<div class="clear"></div>


STYLES FOR THIS:

.postarray {width: 300px;height: auto;padding: 5px;border-bottom: solid 1px black;margin: 10px 0;float: left;display: block; }

.col { width:310px; float:left; margin-left:20px; } /*adjust values*/
#col-1.col { margin-left: 0; } /*optional*/