how to style individual category posts

I’m a newb to WP and I am trying to style homepage posts (not loop) to be in their own container so as to give the posts some separation. Please see url: http://caspca.org/wordpress/ (look at the posts, “Volunteering, “Thank you for being a friend”). This post category has a slug of “home-page-article”

Following what I could gather from Googling this issue, I:

1. added this code to the functions.php file:

/* Style Homepage Article Posts ********************************************/
function the_category_unlinked($separator = ' ') {
    $categories = (array) get_the_category( 'home-page-article' );

    $thelist = '';
    foreach($categories as $category) {    // concate
        $thelist .= $separator . $category->home-page-article;
    }

    echo $thelist;
}

2. added this code to the single.php file:

<div class="post<?php the_category_unlinked('home-page-article'); ?>">

3. then on the homepage (named “template_home.php”), I’m not sure what to add in this code (if anything at all):

<div class="eightcol">
	<?php query_posts('cat=5'); ?>
	<?php while (have_posts()) : the_post(); ?>
	<h2><?php the_title(); ?></h2>
	<?php the_content(); ?>
	<?php endwhile; ?>

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

4. then the sytling is this:

.row .eightcol .home-page-article {
	background-color:#ebebeb;
	padding:10px;
	border:1px solid #CCC;
	-moz-border-radius: 10px;
	border-radius: 10px;
	}

I don’t know php very well at all (as I’m sure is obvious to you), if anyone can tell what I’m doing wrong, much appreciated. Thank you.