About This HTML Issue
A document lacks a heading with a computed level of 1, which means there is no <h1> element (or an element whose final heading level resolves to 1) on the page.
The W3C validator raises this as a warning because every document should have at least one <h1> to identify its main topic. Screen readers and search engines rely on the heading hierarchy to understand page structure, and <h1> is the expected entry point of that hierarchy.
A "computed heading level" differs from the literal tag name only when the now-obsolete <hgroup> algorithm or the abandoned outline algorithm would adjust levels. In practice, for nearly all documents, a computed level of 1 simply means an <h1> tag.
This warning appears when a page uses <h2>, <h3>, or other headings but skips <h1> entirely. Adding a single <h1> that describes the page content fixes the warning.
Example with the warning
<!DOCTYPE html>
<html lang="en">
<head>
<title>My page</title>
</head>
<body>
<h2>About us</h2>
<p>Welcome to our site.</p>
<h3>Our team</h3>
<p>We are a small group.</p>
</body>
</html>
Fixed example
<!DOCTYPE html>
<html lang="en">
<head>
<title>My page</title>
</head>
<body>
<h1>My page</h1>
<h2>About us</h2>
<p>Welcome to our site.</p>
<h3>Our team</h3>
<p>We are a small group.</p>
</body>
</html>
Each page should have exactly one <h1>. If the design calls for the <h1> to be visually hidden (for example, when a logo replaces the text), use a CSS technique to hide it from sighted users while keeping it accessible to screen readers, rather than removing it from the markup.
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