Correct placement of next/previous buttons fixing css

The theme I purchased doesn’t include next/previous buttons at the bottom of my 10 displayed posts. I was trying to add this in, and somehow messed up the css. My two sidebars are now below my posts. Does anyone know how to fix this? My url is: .

And here’s the current code I have for index.php

<?php get_header(); ?>
	<div id="content-wrapper">
		<div id="main-wrapper">
        <div style="clear: both;"></div>
        <div id="main" class="main section">
		<?php if (have_posts()) : ?>
			<?php while (have_posts()) : the_post(); ?>

			<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
				<h3><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_title(); ?></a></h3>
                <h1 class="post-comment-link"><a class="comment-link" href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php comments_popup_link('0', '1', '%'); ?></a></h1>
				<h2 class="date-header"><?php the_time('d.n.y') ?></h2>
				<div class="post-body entry-content">
					<?php the_content(); ?>
				</div>
				<div class="post-footer"><?php comments_popup_link('0 comments', '1 comment', '% comments'); ?> <span class="post-footer-cat">categories: <?php the_category(', ') ?></span><span class="post-footer-social"><a href="http://twitter.com/home?status=Currently reading: <?php the_title ();?> <?php echo get_settings('home'); ?>/?p=<?php the_ID(); ?>" target="_blank"><img src="<?php bloginfo('template_url'); ?>/images/postfooter-twitter.png" /></a><a href="http://www.facebook.com/sharer.php?u=<?php the_permalink() ?>" target="_blank"><img src="<?php bloginfo('template_url'); ?>/images/postfooter-facebook.png" /></a><a href="javascript:void((function(){var%20e=document.createElement('script');e.setAttribute('type','text/javascript');e.setAttribute('charset','UTF-8');e.setAttribute('src','http://assets.pinterest.com/js/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)})());"><img src="<?php bloginfo('template_url'); ?>/images/postfooter-pinterest.png" /></a></span></div>
				<div class="clear"></div>

			<?php endwhile; ?>
			<?php include (TEMPLATEPATH . '/navigation.php'); ?>
		<?php else : ?>
			<h2 class="page_header center">Not Found</h2>
			<div class="entry">
				<p class="center">Sorry, but you are looking for something that isn't here.</p>
				<?php get_search_form(); ?>
			</div>
		<?php endif; ?>
		<?php include (TEMPLATEPATH . '/l_sidebar.php'); ?>
    	<?php include (TEMPLATEPATH . '/r_sidebar.php'); ?>
    </div>
<?php get_footer(); ?>