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Hi Simon, The goal of HTML validation should be to ensure your web pages will display properly in all major browsers, devices (iPads, smartphones, etc) and can be crawled properly by search engines. The goal is not necessarily to get the green "This document was successfully checked as ...." badge. In brief, the w3c validator tool has not been designed to handle that specific metadata. The issue has been reported as a bug and, while the bug has been marked as "fixed", a solution has not been offered yet. For now you can either use validator.nu or Google's Rich Snippets testing tool to test your microdata. If you yearn for the green "valid code" stamp you can move your microdata to javascript although that action simply hides the code from the validator tool. Your code is no more or less valid either way.