Setting a Drupal Administration Theme
The Drupal theme you set as the default is the active theme for the entire Drupal site. You can, however, also set a different theme that appears only on the site administration pages when you’re logged in as an administrator. This allows you to tinker with the site theme and layout while retaining the capability to reset the site theme should something go horribly wrong with the design.
Having stuff that still works as it should when everything else goes wrong is a very, very good thing. You want this. To set a different theme for the site administrator pages, follow these steps:
From the Dashboard menu bar, click Appearance to open the Appearance overlay.
Scroll to the bottom of the overlay and locate a pane titled Administration Theme.
Choose your preferred theme from the drop-down list.
You can also enable this theme when you post or edit content by selecting the Use Administration Theme for Content Editing check box.
Click the Save Configuration button.
You now have a theme selected that only appears when you’re logged in as the site administrator.