http://dev.harveys.co.uk/clients/
clients { margin-right:-20px; }
clients .client { float:left; background:#9d9fa2; width:190px; margin:0 8px 8px 0; }
clients .client .inner { min-height:80px; }
.inner { padding:10px; }
clients .last-child { margin-right:0; }
clients .client img { margin-bottom:5px; border:1px solid #aaa; }
<div id="page">
    <div id="clients" class="clearfix">
        <?php $count = 0;?>
        <?php query_posts('category_name=Clients&showposts=20&orderby=297,299,308,302,304'); if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>  
        <?php $count++; ?>
        <div class="client <?php if ( $count % 3 == 0 ){ echo "last-child"; }?>">
<div class="inner">
    <img src="" alt="" width="168" height="104" alt="" /></a>
    <h2></h2>               
    </div><!-- clients -->
    </div><!-- page -->