Sidebar validation issues

The problem was some code that I think I largely copied from another post on the forum — but maybe I messed it up myself. The nonvalidating version was:

<ul><?php query_posts('cat=6&order=ASC&showposts=-1'); ?>
<?php if(have_posts()) : while(have_posts()) : the_post(); ?>
<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
<?php endwhile; endif; ?></li>
</ul>

Which should have read:

<ul><?php query_posts('cat=6&order=ASC&showposts=-1'); ?>
<?php if(have_posts()) : while(have_posts()) : the_post(); ?>
<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endwhile; endif; ?>
</ul>

It was the </li> that was the problem.

It was interesting how one glitch could cause multiple instances of nonvalidation.