Where To Place Adsense Code In My Header?

[yaskevic]

Please take a look at the above image. I'd like to replace a blue rectangle with an adsense ad. Below is my header. Could you tell me please what should I replace with adsense code in order for adsense ad to be shown instead of a blue rectangle? Thank you in advance. Here is my header code :

<table width="100%" align="center" border="0" cellspacing="0" cellpadding="0">
   <tr>
    <td style="background: url($stylevar[imgdir_misc]/nav_bg.gif) repeat-x center center;">$header_advertisement</td>
       </tr>
      </table>
<table width="100%" align="center" border="0" cellspacing="0" cellpadding="0" style="background: url(images/bigred/gradients/gradient_nav.gif) repeat-x;">
        <tr> 
          <td><a href="index.php"><img src="$stylevar[imgdir_misc]/home.gif" alt="" border="0" /></a></td>
          <td><a href="usercp.php"><img src="$stylevar[imgdir_misc]/usercp.gif" alt="" border="0" /></a></td>
          <td><a href="memberlist.php"><img src="$stylevar[imgdir_misc]/members.gif" alt="" border="0" /></a></td>
          <td><a href="search.php$session[sessionurl_q]" accesskey="4" rel="nofollow"><img src="$stylevar[imgdir_misc]/search.gif" alt="" border="0" /></a></td>
          <if condition="$bbuserinfo['userid']">
      <td id="usercptools"><img src="$stylevar[imgdir_misc]/quick.gif" alt="" border="0" /><script type="text/javascript">vbmenu_register("usercptools", true); </script></td></if>
          <if condition="$show['registerbutton']">
      <td><a href="register.php$session[sessionurl_q]" rel="nofollow"><img src="$stylevar[imgdir_misc]/register.gif" alt="" border="0" /></a></td>
        </if>
        </tr>
      </table>
<table width="100%" align="center" border="0" cellspacing="0" cellpadding="0">
    <tr style="height: 15px;">
        <td colspan="3" style="background: #610000;">$header_advertisement</td>
    </tr>
    <tr style="height: 110px;" valign="top">
        <td width="191"><img src="$stylevar[imgdir_misc]/logo.gif" alt="" /></td>
        <td style="background: url('$stylevar[imgdir_misc]/ad_bkg.gif') no-repeat;" width="542"><img src="$stylevar[imgdir_misc]/banner.gif" alt="banner" style="display: block; margin: 29px 0px 0px 40px;" /></td>
<td style="background: url(images/bigred/gradients/gradient_banner.gif) repeat-x;">$header_advertisement</td></tr>
                </tr>
<table width="100%" align="center" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td background="$stylevar[imgdir_misc]/nav_bg.gif"><img src="$stylevar[imgdir_misc]/nav_bg.gif" alt="" width="738" height="38"></td>
  </tr>
</table>
<!-- content table -->
$spacer_open
$leftcolumn_advertisement
$_phpinclude_output

Waiting for your help