When developing a Drupal website, you may be interested in having content specific templates, so different kind of pages do not look the same. By default, we can use list of default core templates, but we can adapt it better to meet our needs by modifying template.php file in theme folder (we are assuming we are using PHPTemplate Theme engine). In my case, using an Acquia theme, I noticed it ignored page-content_type.tpl.php templates.