title: NoReverseMatch at / error in django after url template tag usage
body: <p>I am having this error after using the template <code>{% url %}</code> tag,</p>
  
  <pre><code>NoReverseMatch at /index/
  
  Reverse for 'index' with arguments '()' and keyword arguments '{}' not found. 0 pattern(s) tried: []
  </code></pre>
  
  <p>this happened when I changed <code>href="index"</code> to <code>href="{% url 'index' %}"</code>.</p>
  
  <p>my url is</p>
  
  <pre><code>url(r'^index/$', views.index, name='index'),
  </code></pre>
  
  <p>I tried to remove <code>$</code> but still the same error?</p>