You cannot access the session cookie because it is set to HTTPOnly by default (you can see it with Firebug (Resource-> Cookies-> sessionid HTTP column))
Copying from docs :
SESSION_COOKIE_HTTPONLY
Default: True
Whether to use HTTPOnly flag on the session cookie.
If this is set to True, client-side JavaScript will not to
be able to access the session cookie.
: SESSION_COOKIE_HTTPONLY = False settings.py, . .