def primary_avatar(user, size=AVATAR_DEFAULT_SIZE):
    """
    This tag tries to get the default avatar for a user without doing any db
    requests. It achieve this by linking to a special view that will do all the 
    work for us. If that special view is then cached by a CDN for instance,
    we will avoid many db calls.
    """
    alt = unicode(user)
    url = reverse('avatar_render_primary', kwargs={'user' : user, 'size' : size})
    return """<img src="%s" alt="%s" />""" % (url, alt,
        )
This tag tries to get the default avatar for a user without doing any db
    requests. It achieve this by linking to a special view that will do all the 
    work for us. If that special view is then cached by a CDN for instance,
    we will avoid many db calls.