Special if statement for main page

I have a worpress blog, that I like to have my rectangle ad run on all pages except the home page. (on www.bradsblog.net)

What code can I add to make this work. I currently do not have a seperate post/main template. Here is my current snippett:

<?php  get_header(); ?>
<?php get_sidebar(); ?>
<hr />
<!-- google_ad_section_start -->


<div id="content">
<script type="text/javascript"><!--
google_ad_client = "pub-1725522918851661";
google_ad_width = 336;
google_ad_height = 280;
google_ad_format = "336x280_as";
google_ad_type = "text_image";
google_ad_channel ="5657200493";
google_color_border = "FFFFFF";
google_color_bg = "FFFFFF";
google_color_link = "008000";
google_color_url = "000000";
google_color_text = "000000";
//--></script>
<script type="text/javascript"
  src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

    <?php // Post dates off by default the_date('','<h2>','</h2>'); ?>
    <div id="post-<?php the_ID(); ?>">
    <h2><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h2>    
    <div class="meta"><?php _e("Posted in"); ?> <?php the_category(',') ?> by <?php the_author() ?> on the <?php the_time('F jS, Y') ?> <?php edit_post_link(__('Edit This')); ?></div>
    <div class="main">
        <?php the_content(__('(more...)')); ?>
    </div>
    </div>
<!-- google_ad_section_end -->
     <div class="related">

<b><u><h3>Related Posts</h3></b></u><br>
<?php related_posts(5, 10, '<li>', '</li>', '', '', false, false); ?>
   
      </div> 
      <br>
    <div class="comments">
        <?php wp_link_pages(); ?>
        <?php comments_popup_link(__('<strong>0</strong> Comments'), __('<strong>1</strong> Comment'), __('<strong>%</strong> Comments')); ?>

Code (markup):