This can be done by something like:
<example_url url="..." should_not_select="true" />
Also, the unit test that exercises and verifies all example_urls being selected by the corresponding selector should be updated, acknowledging this new attribute.
One use case is: the <imdb_movie> selector should not select this URL (it used to): http://www.rottentomatoes.com/m/django_unchained_2012/trailers/