Error message

• Warning: unlink(/var/www/html/wwwroot/drupal_47169/sites/default/files/css/follow.css): Permission denied in drupal_unlink() (line 2202 of /var/www/html/wwwroot/drupal_47169/includes/file.inc).
• Warning: unlink(/var/www/html/wwwroot/drupal_47169/sites/default/files/css/follow.css): Permission denied in drupal_unlink() (line 2202 of /var/www/html/wwwroot/drupal_47169/includes/file.inc).