代码来自这里：
base.html
<html>
<head>...</head>
<body>
...
{% block nav %}
<ul id="nav">
<li>{% block nav-home %}<a href="{% url home %}">Home</a>{% endblock %}</li>
<li>{% block nav-about %}<a href="{% url about %}">About</a>{% endblock %}</li>
<li>{% block nav-contact %}<a href="{% url contact %}">Contact</a>{% endblock %}</li>
</ul>
{% endblock %}
...
</body>
</html>
about.html
{% extends "base.html" %}
{% block nav-about %}<strong class="nav-active">About</strong>{% endblock %}
PS: vim多行缩进的方法是选中对应行，按"<"以及">"，按"=="可将选中的行进行自动缩进。