Google Now Sends Duplicate Content Warning

Google has announced they will begin notifying you if and when they make a cross-domain URL decision involving your site. When similar or duplicate content is present across more than one domain, Google chooses one of the URLs to index. When this cross-domain URL decision is made, some of your content may not be getting indexed in favor of another URL.

While there are multiple reasons, some bad and some not so bad, for there to be duplicate information on more than one domain, it's never good when you're on the losing end of the deal. This is why Google has decided to send you a notification when they need to make this decision. So, as of now, they leave you to figure out and resolve the problem.

Currently Google only sends the notification to you within Webmaster Tools. So, be sure your site is claimed within Webmaster Tools and have it set up to send you an email regarding all new notifications that come in.