Попробывал написать без пароля и вот что вышло:
Page not found (404)Request Method: GET
Request URL:
http://djangoproject.su/forum/topic/5/post/add/forum/account/signin/?next=/forum/topic/5/post/add/
Using the URLconf defined in urls, Django tried these URL patterns, in this order:
^$
^admin/
^forum/account/
^forum/ ^$
^forum/ ^(?P<forum_id>\d+)/$
^forum/ ^moderate/(?P<forum_id>\d+)/$
^forum/ ^search/$
^forum/ ^misc/$
^forum/ ^user/(?P<username>.*)/$
^forum/ ^users/$
^forum/ ^topic/(?P<topic_id>\d+)/$
^forum/ ^(?P<forum_id>\d+)/topic/add/$
^forum/ ^topic/(?P<topic_id>\d+)/delete_posts/$
^forum/ ^topic/(?P<topic_id>\d+)/move/$
^forum/ ^topic/(?P<topic_id>\d+)/stick/$
^forum/ ^topic/(?P<topic_id>\d+)/unstick/$
^forum/ ^topic/(?P<topic_id>\d+)/close/$
^forum/ ^topic/(?P<topic_id>\d+)/open/$
^forum/ ^topic/(?P<topic_id>\d+)/post/add/$
^forum/ ^post/(?P<post_id>\d+)/$
^forum/ ^post/(?P<post_id>\d+)/edit/$
^forum/ ^post/(?P<post_id>\d+)/delete/$
^forum/ ^preview/$
^forum/ ^subscription/topic/(?P<topic_id>\d+)/delete/$
^forum/ ^subscription/topic/(?P<topic_id>\d+)/add/$
^forum/ ^pm/new/$
^forum/ ^pm/outbox/$
^forum/ ^pm/inbox/$
^forum/ ^pm/show/(?P<pm_id>\d+)/$
^forum/ ^reputation/(?P<username>.*)/$
^forum/ ^attachment/(?P<hash>\w+)/$
^feeds/(?P<url>.*)/$
^static/(?P<path>.*)$
The current URL, forum/topic/5/post/add/forum/account/signin/, didn't match any of these.
You're seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.