EDIT

  if (!path_is_admin(current_path())) {

    //FIXME To add CSS or JS that should be present on all pages, modules

    //      should not implement this hook, but declare these files in their .info file.

    drupal_add_css(drupal_get_path('module', 'cdm_dataportal') . '/cdm_dataportal.css');

    // drupal_add_css(drupal_get_path('module', 'cdm_dataportal').'/cdm_dataportal_print.css', 'print');

    drupal_add_css(drupal_get_path('module', 'cdm_dataportal') . '/cdm_dataportal_screen.css', array('type' => 'screen'));

  }