<p><a href="/admin/build/skinr/page">Page rules</a> allow you to use Skinr to
  add body classes to your page(s) based on user role, path, or PHP code, just
  like block visibility settings. They can be used to do things like: set a
  container width for grids, define sections of a site, change font size/face,
  background colors, etc.
</p>