There is a special header to allow or disallow showing page inside i-frame - X-Frame-Options
It's used to prevent an attack called clickjacking. You can check the Django's doc about it https://docs.djangoproject.com/en/dev/ref/clickjacking/
Sites that want their content to be shown in i-frame just don't set this header.
I think in your installation of Django this protection is turned on by default. If you wan't to allow embedding your content inside i-frames you can either disable the clickjack protection in your settings for the whole site, or use per view control with django.views.decorators.clickjacking
decorators:
xframe_options_exempt
xframe_options_deny
xframe_options_sameorigin
Per view control is a better option.