if media/ is your project media directory, then in the template use
<link href="{{ MEDIA_URL }}base.css" rel="stylesheet" type="text/css" />
this is considering you have passed RequestContext to your template,
ex:
def some_view(request):
# ...
return render_to_response('my_template.html',
my_data_dictionary,
context_instance=RequestContext(request))
You will also need to have static urls served when running on the localdev server.
Include this in your urls.py:
from django.conf import settings
if settings.DEBUG:
urlpatterns += patterns('',
url(r'^%s(?P<path>.*)$' % settings.MEDIA_URL[1:],
'django.views.static.serve',
{'document_root': settings.MEDIA_ROOT, 'show_indexes': True})
)