(Reuters) - 

Some advertisers are working overtime to scrub their spots from websites including Breitbart News, an unintended consequence of the automated ad buying systems that are meant to lower costs and allow for more targeted advertising.

Those trying to keep their ads off certain websites are finding they must take steps to verify the spots they bid for are where ads actually appear and that there are no third parties involved that can result in ads winding up in unintended places.

Breitbart News, once run by U.S. President Donald Trump's chief strategist Steve Bannon and popular with the alt-right, a loose grouping characterized by a rejection of mainstream politics that includes neo-Nazis and anti-Semites, has become a particular concern for some advertisers and the automated exchanges they work with.

While the exact number of advertisers that have blacklisted Breitbart is unknown, Sleeping Giants, an anonymous group campaigning on Twitter against companies advertising on the website, puts the number higher than 1,500.

More »