W3C HTML DTD Validation Web Standard

HTML code can be automatically validated against a formal description of the HTML language in a DTD (Document Type Definition). The formal description lists elements and attributes, along with rules on how they can be combined.

• W3C HTML DTD Validation

Rules

• Nested a element
• Nested button element
• Nested label element
• Nested form element
• Nested image map
• Unknown entity name
• Reference to missing ID
• HTML validation error
• No DOCTYPE
• Doctypes Invalid DOCTYPE
• HTML 5 HTML 5 doctype