Error in image.html template

[Anber]

<img {% if object.float %}class="{{ object.float }}" {% endif %}alt="{% if object.alt %}{{ object.alt }}{% endif %}" src="{% thumbnail object.image image_size %}" />

but context.update({ 'picture':instance, 'link':link, 'image_size': u'%sx%s' % (width, height), 'placeholder':placeholder })