How do I highlight a link based on the current page?

<a id="active" href="thisPage.html">this page</a>

a#active { color: yellow; }

<!-- base.html -->
...
<body class="{% block bodyclass %}{% endblock %}">
...
<div id="nav">
  <ul>
    <li id="nav-questions"><a href="{% url questions %}">Questions</a></li>
    <li id="nav-tags"><a href="{% url tags %}">Tags</a></li>
    <li id="nav-users"><a href="{% url users %}">Users</a></li>
    <li id="nav-badges"><a href="{% url badges %}">Badges</a></li>
    <li id="nav-ask-question"><a href="{% url ask_question %}">Ask Question</a></li>
  </ul>
</div>

<!-- questions.html -->
{% extends "base.html" %}
{% block bodyclass %}questions{% endblock %}
...

body.questions #nav-questions a,
body.tags #nav-tags a,
body.users #nav-users a,
body.badges #nav-badges a,
body.ask-question #nav-ask-question a { background-color: #f90; }

body.questions #questionsTab
{
    color: #f00;
}

// assuming this JS function is called when page loads
onload()
{
  if (location.href.indexOf('/questions') > 0)
  {
    document.getElementById('questionsLink').className = 'questionsStyleOn';
  }
}