The djpcms/960gs/standard.html specializes your root template by creating inside the html-container tag three subtags:
{% block html-container %}
<div id="branding-banner">{% block page-branding %}{% endblock %}
</div>
{{ grid.clear }}
<div id="site-navigation-banner">
<div class="{{ grid.column1 }}">{% block site-navigation %}{% endblock %}
</div>
</div>
{{ grid.clear }}
<div id="main-body">
{% if cl.title %}{% block page-headings %}
<div class="{{ grid.column1 }}">
<h2 id="page-heading">
{{ cl.title }}
</h2>
</div>
{{ grid.clear }}{% endblock %}{% endif %}
{% block page-prebody %}{% endblock %}
{% block page-body %}{% endblock %}
{% block page-postbody %}{% endblock %}
</div>
<div id="footer">{% block page-footer %}{% endblock %}
</div>
{% endblock %}