I prefer not to turn DEBUG off. Instead I put the following snippet in the urls.py:
if settings.DEBUG:
urlpatterns += patterns('',
(r'^500/$', 'your_custom_view_if_you_wrote_one'),
(r'^404/$', 'django.views.generic.simple.direct_to_template', {'template': '404.html'}),
)
In the snippet above, the error page uses a custom view, you can easily replace it with Django’s direct_to_template view though.
Now you can test 500 and 404 pages by calling their urls: http://example.com/500 and http://example.com/404