If you take a look at post.html, there’s a potential problem with the author link. We link to the author’s home page, but homepage is an optional field. If the author doesn’t have a home page, that link will just go to the same page.
There’s a template tag for “if” to help with situations like this.
<p class="author">
{% if post.author.homepage %}
<a href="{{ post.author.homepage }}">{{ post.author }}</a>,
{% else %}
{{ post.author }}
{% endif %}
{{ post.date|date:"l, F jS, Y h:i a" }}
</p>
You can find other “ifs” at http://docs.djangoproject.com/en/dev/ref/templates/builtins/.