Do I have to write {% load staticfiles %} when importing CSS files in my Django templates using {{ STATIC_URL }} template tag
<link href="{{ STATIC_URL }}abc/xyz/form.css" rel="stylesheet" type="text/css">
No, all you need is 'django.template.context_processors.static' included in the context_processors section of the TEMPLATES' OPTIONS in your settings.py.
<script src="{% static 'common/js/jquery.js' %}" type="text/javascript"></script>{% load static %} or {% load staticfiles %} is necessary - nb. in Django 1.10 {% load staticfiles %} exists for backward compatibility and will probably be deprecated in 2.0.