How to avoid using JS to render a layout

This WP theme (live preview) uses Javascript to make round corners etc. But it just slows down the page so I want to remove it. Any idea how to replace it with CSS which will work in the same way?

<script type="text/javascript" src="http://www.google.com/jsapi"></script>
<script type="text/javascript">
	// Load jQuery
	google.load("jquery", "1.2.6");
</script>
<script type="text/javascript">
/* <![CDATA[ */
	var $j = jQuery.noConflict();
	$j(document).ready(function() {
		$j(".menu a").wrapInner(document.createElement("span")); 
		$j('.post').before('<div class="post_top"></div>').after('<div class="post_end"></div>');
		$j('.widget').before('<li class="widget_top"></li>').after('<li class="widget_end"></li>');
		$j('#search').prepend('<h2 style="text-align: left;">Search</h2>');
	});
/* ]]> */

HTML:

 

Could someone please help me?