Missed HTML syntax error in Nu Html Checker

I loaded the following code into the text input field of the Nu Html Checker, at <https://validator.w3.org/nu/#textarea>, and clicked the Check button. It reported “Document checking completed. No errors or warnings to show.”

<!DOCTYPE html>
<html lang="en-US">
    <head>
        <title>Town of Wilton, NH Zoning Board of Adjustment</title>
    </head>
<body>
    <header>
        <a href="index.html">
            <img src="Imgs/town_hall_logo.gif" alt="" title="Wilton Town Seal" width="80" height="78">
            <h1>Town of Wilton, NH Zoning Board of Adjustment</h1>
        </a>
    </header>
    <main>
        <p>This is the web site of the Wilton, NH Zoning Board of Adjustment.</p>
    </main>
</body>
</html>

Note the nesting structure <a><img><h1></h1></a>.

If I read the HTML5 spec correctly, the content of an <a> element must be phrasing content, and an <h1> element is not phrasing content. Therefore, I would have expected the checker to report an error.

Thank you,
Neil Faiman

Received on Tuesday, 28 April 2026 13:15:13 UTC