http://www.blogduster.com/google-data-highlighter/ Data Highlighter is a webmaster tool for teaching Google about the pattern of structured data on your website.Then Google can present your data more attractively and in new ways in search results and in other products such as the Google Knowledge Graph. For example, if your site contains event listings you can use Data Highlighter to tag data (name, location, date, and so on) for the events on your site. The next time Google crawls your site, the event data will be available for rich snippets on search results pages. Note that Data Highlighter can only access pages that have been crawled by Google recently. If Google hasn't crawled or can't crawl some of your pages, such as pages behind sign in forms, you can't use Data Highlighter for those pages.