Use stats.co-ment.com for piwik optout iframe rather than piwik.sopinspace.net so SSL certificate is valid.
{% extends "site/layout/base.html" %}
{% load i18n %}
{% block content %}
<h1>404: {% blocktrans %}Page not found{% endblocktrans %}</h1>
{% blocktrans %}The requested page could not be found.{% endblocktrans %}
{% endblock %}