HTML Checking for Large Sites

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

A <header> element can’t include other <header> elements inside.

The header element represents a group of introductory or navigational aids, as in this example:

<body>
  <header>
    <h1>Welcome to our Shop</h1>
    <nav>
      <ul>
        <li><a href="/toys">Toys</a>
        <li><a href="/books">Books</a>
        <li><a href="/shoes">Shoes</a>
      </ul>
    </nav>
 </header>

 <p>Main content...</p>
</body>

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Related W3C validator issues