Move contrast checking into Python

Change banner size dependent on group content
Tidy up inline JS for some files
Correct spelling

gallery/templates/error.html

@@ -1,8 +1,7 @@
 {% extends 'layout.html' %}
-
 {% block content %}
     <span class="error-page">
         <h1>{{error}}</h1>
         <p>{{msg}}</p>
     </span>
-{% endblock %}
+{% endblock %}