Static Page and previous article not shown

Dear Experts,
pls visit,
http://wwwinspireasia.com/wp-content/themes/contractor/civil-projects.php

why if i click previous entries, the article is not change ?

this is my code :

<?php query_posts(‘cat=15&showposts=3’); ?>
<?php while (have_posts()) : the_post(); ?>
<?php if ( in_category(15) ) { ?>
<?php the_content(); ?>
<div class=”navigation”>
<div class=”alignleft”><?php next_posts_link(‘« Previous Entries’) ?></div>
<div class=”alignright”><?php previous_posts_link(‘Next Entries »’) ?></div>
</div>
<?php } else {
}; ?>
<?php break; ?>
<?php endwhile; ?>

Pls help Sir