HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

Start tag seen without seeing a doctype first. Expected “<!DOCTYPE html>”.

HTML documents are expected to start with a first line containing the Document Type Declaration, that defines the HTML version used. Since HTML5, it’s just <!DOCTYPE html>, which must appear before the start <html> tag.

Here’s an example of a minimal HTML5 document:

<!DOCTYPE html>
<html>
  <head>
    <title>Test</title>
  </head>
  <body>
    <p></p>
  </body>
</html>

Related W3C validator issues