fluxappeal on "Adding input button throws off width in Twenty Twelve"

A simple task of adding a button to the bottom of a custom template is throwing off the width of my content area. I added the code after the loop, and tried it with and without divs, but I can't get the page to go full width. The entire content area cuts off.

Here's the page: http://www.arthurtaussig.com/test-purchase-button/
and the code:

get_header(); ?>

	<div id="primary" class="site-content">
		<div id="content" role="main">

			<?php while ( have_posts() ) : the_post(); ?>
				<?php get_template_part( 'content', 'page' ); ?>
				<?php comments_template( '', true ); ?>
			<?php endwhile; // end of the loop. ?>

            <div class="container clearfix">

                <div class="button_purchase">

          		  <a href="url-link-here"><input type="button" value="Purchase" class="button_purchase" /></a>

                </div><!-- #button_purchase -->

           </div><!-- #clearfix -->

      </div><!-- #content -->

	</div><!-- #primary -->

<?php get_footer(); ?>

I'm sure it's something obvious, but it escapes me. Thank you ;)