How do I add a custom style to node by its type? I've tried following the instructions on http://drupal.org/node/1089656, but I somehow can't get it right.

How do I apply custom layout/style to a node based on its type?
If the content type of the node is Article, then the template file Drupal looks for is node--article.tpl.php.
If the content type name contains underscores, those are replaced with hyphens. If the content type machine name is snippet_code, then the template filename is node--snippet-code.tpl.php.