Drupal has many well documented best practices, many of which we've covered here previously. From using Features to export all site configuration, to applying updates on a copy of the site instead of production, to using a modern responsive base theme, there is usually a tried & trusted process for most scenarios that can help keep sites stable, and editorial teams & visitors happy. There are, however, some (very, very, very) rare occasions when it can be necessary to break with convention, cause designers & developers to pull their hair out and run around screaming, and allow the editorial team to add custom CSS (or JavaScript) to individual pages. The Code-per-Node module provides a structured, reliable and easy-to-use solution for these occasions.