Modifying the Drupal Admin Theme

It is customary, when modifying a theme, to set it as the default theme for the website in use, in order to see the results of any changes. But it is dangerous to employ that same theme for admin, because if those changes break the theme so badly that it cripples the functionality of the site, then it may be quite difficult to recover. As a precaution, set the admin theme to one known to be stable — such as Seven or Garland — prior to making any drastic changes. Thus, even if the public pages break, the admin pages should still work.