Be sure to include the appropriate DOCTYPE declaration for the form. Use the W3C validator for strict HTML or XHTML or a test validator for HTML5. The code for the seal is available on the w3c validator site and can be copied to your form page. The seal is a live link and when clicked it will resubmit the page for validation. It will only give a 'green light' to [that is, passed validation] if the page is correct.