A good question was brought up in the Google Webmaster Help Forum: Should I add “no-follow” to my banner ads? In-short, maybe. It ultimately depends on where these ads are coming from in the first place. For example most advertising programs such as Comission Junction will send all their links through a URL which is specified as a no-follow via a robots.txt file – that way your impressions do not get messed up by search engine bots. However if you’re using your own advertising system – chances are you will need to add a no-follow to your ads. Check out Google’s detailed answer in the video below:
Michael Boguslavskiy is a full-stack developer & online presence consultant based out of New York City. He's been offering freelance marketing & development services for over a decade. He currently manages Rapid Purple - and online webmaster resources center; and Media Explode - a full service marketing agency.