Sidebar style issue

Hi everyone,
I designed the search result page so the content is on the left and the sidebar is on the right.
when I search something and I got search result, everything goes well, the style is rendered properly exactly the way I intended, but if there’s no search result something weird happen, I get the content on the left and instead of getting the sidebar on the right it becomes under the content !!
here’s my php code:

<?php get_header(); ?>
	<div class="main-content-wrap">
		<div id="content-holder">
			<div class="left-side">
				<div class="search-result">
						<h2>Search Result:</h2>

						<ul>
								<?php if(have_posts()) : while(have_posts()) : the_post();?>
								<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
								<?php endwhile; ?>
						</ul>

				</div><!-- end search result -->
				<div id="morePrev">
					<?php next_posts_link('More...'); ?>
					<?php previous_posts_link('Return...'); ?>
				</div>

			<?php else: ?>
			<p>no posts</p>
			<?php endif; ?>
			</div><!-- end left side -->
<?php get_sidebar(); ?>
		</div><!-- end conetent holder -->
	</div><!-- end main content wrap -->
<?php get_footer(); ?>

and here is my CSS

.main-content-wrap{
width: 100%;
float: left;
overflow: hidden;
background: transparent;
}

#content-holder {
width: 1000px;
overflow: hidden;
margin-right: auto;
margin-left: auto;
}

.left-side{
width: 680px;
float: left;
overflow: hidden;
background-color: #fff;
}

#morePrev {
margin-top: 20px;
width: 600px;
overflow: hidden;
margin-right: auto;
margin-left: auto;
}

div#morePrev a:first-child {
float: right;
}

div#morePrev a:last-child {
float: left;
}

.sidebar{
width: 300px;
float: left;
margin-left: 20px;
overflow: hidden;
background-color: rgb(250, 250, 250);
}

.search-result {
float: left;
width: 650px;
overflow: hidden;
border: 2px solid #cecece;
padding-bottom: 20px;
margin-top: 30px;
margin-bottom: 20px;
}

.search-result h2 {
float: left;
display: block;
width: 100%;
}

.search-result ul {
list-style-type: none;
float: left;
margin-top: 30px;
margin-left: 60px;
}

.search-result ul li {
display: block;
}

any ideas?