At some point, most developers have found that, despite their best efforts, one of their staging or develoment sites has been found by Google or other search engines. Usually, this is because we must make the work available for preview to the client before the site goes live to the world. Without careful planning, it can be tricky to show a staging site to a client, but not to Google. Do not assume that, because you haven't submitted a URL to search engines, they won't find your site. Take proactive measures to keep your dev and staging sites out of search engines.