added ADMINS constant to base.py, this constant contains a tuple of admin email addresses. Django will send email to admins in this list when a 500 server error occurs. Also added 'django.middleware.common.BrokenLinkEmailsMiddleware' to the middleware classes block, this allows Django to email admins when a 404 occurs. There is also a commented out block called IGNORABLE_404_URLS which can be used to filter out noncritial 404 errors from being emailed. Also added text to the 403, 404, and 500 templates.