Center 404 copy in a janky way :)

Author: ericholscher

readthedocs/donate/templates/donate/promo_404.html

@@ -11,6 +11,7 @@
 {% endblock %}
 
 {% block content %}
+<div style="margin-left: auto; margin-right: auto; width: 900px; text-align: center">
     {% if suggestion %}
       <div class="suggestions">
           <h1>You've found something that doesn't exist.</h1>
@@ -41,4 +42,5 @@ <h1>
 <p>
 Read the Docs is sponsored by <a href="{{ promo_data.link }}">Sentry</a>, which gives developers the tools to keep calm when things catch fire.
 </p>
+</div>
 {% endblock %}