Google has just added a new structured data tab to Webmaster Tools. This tab detects structured data markup (all structured data types) on your website and tells you how Google evaluated it. As well you can use their structured data markup tool (Google structured data markup helper), to test and fix bad markup code.
As we can see this new tab falls under the content keywords tab.
Google Structured Data Tab for Tracking You Structured Data Markup
Google describes rich snippits (structured data markup) in the following way.
“If Google understands the content on your pages, we can create rich snippets—detailed information intended to help users with specific queries. For example, the snippet for a restaurant might show the average review and price range; the snippet for a recipe page might show the total preparation time, a photo, and the recipe’s review rating; and the snippet for a music album could list songs along with a link to play each song. These rich snippets help users recognize when your site is relevant to their search, and may result in more clicks to your pages.”
“You can help Google surface this relevant information by adding additional HTML markup to your pages. This markup helps Google recognize certain types of data and display it usefully in rich snippets.”