Attribute values
A media query, a language tag, a date, an image candidate string, a URL and an input type, each rejected with the offending value.
Attribute values
examples/showcase/attribute-values.html<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Attribute values</title>
<link rel="stylesheet" href="print.css" media="print and (">
</head>
<body>
<p lang="en_US">Underscore in a language tag.</p>
<p>Published <time datetime="2026-13-01">in month thirteen</time>.</p>
<img src="hero.png" srcset="hero.png 1x, hero@2x.png 2y" alt="Hero">
<a href="https://exa mple.com/">Space in the host</a>
<input type="colour" name="accent" aria-label="Accent">
</body>
</html>error 6:3 schema.html5 invalid value `print and (` for attribute `media` at 6:3 error 9:3 schema.html5 invalid value `en_US` for attribute `{http://www.w3.org/XML/1998/namespace}lang` at 9:3 error 10:16 schema.html5 invalid value `2026-13-01` for attribute `datetime` at 10:16 error 11:3 schema.html5 invalid value `hero.png 1x, hero@2x.png 2y` for attribute `srcset` at 11:3 error 12:3 schema.html5 invalid value `https://exa mple.com/` for attribute `href` at 12:3 error 13:3 schema.html5 invalid value `colour` for attribute `type` at 13:3 6 errors, 0 warnings