Provide variable to page.tpl.php to mark page as Access Denied or 404? Ideally I'd like to provide new classes to the body tag such a access-404 or access-denied, but unfortunately I'm not really aware of how to capture these.

I don't mind to identify these pages from the Page Title itself from template_preprocess_page, however it seems that $vars['title'] does not exist in D7? How can I access the page title from within a template_preprocess function?

SOLUTION: Thanks to DeeZone:

In my template.php:

function template_preprocess_html(&amp;$vars){
  $status = drupal_get_http_header("status");
  switch($status){
  case "403 Forbidden":
  case "404 Not Found";
    $vars['classes_array'][] = 'drupal-page-error';
    dsm($vars);
    break;
  }
}
If I uderstand your question perhaps try: Drupal 7 Custom 404 Page Template - use this method to setup a custom page template (tpl) file for your 404 page. This will give you a specific page template that you can hard code classes you're wanting - "access-404" or "access-denied" in the body tag.