Conversion tracking code immediately after body tag?
You can do this in template.php by using theme_preprocess_html()

function mytheme_preprocess_html(&amp;$vars) {
  $arg = arg();
  $vars['checkout_tracking_script'] = '';
  if (count($arg) == 3 &amp;&amp; $arg[0] == 'checkout' &amp;&amp; $arg[1] == 'complete' &amp;&amp; is_numeric($arg[2])) {
    $vars['checkout_tracking_script'] = '&lt;script&gt;myScript&lt;/script&gt;';
  }
}


Then in your html.tpl.php you can print your script like this.

&lt;?php if ($checkout_tracking_script): ?&gt;
  &lt;?php print $checkout_tracking_script; ?&gt;
&lt;?php endif ?&gt;