W3C HTML Validator Invalid (2011)

By Xah Lee. Date: . Last updated: .

The W3C HTML Validator is getting annoying.

Doesn't Support Data URI Scheme

as of 2014-07-24, the W3C CSS validator doesn't support CSS Data URI Scheme .

w3c css validation data uri scheme fail 2014-07-24
W3C CSS validation, data URI scheme fail

Here is the sample file:

a.amz {background:url(data:image/png;base64,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) no-repeat left center;
background-size:16px 16px;
padding-left:19px;
border:solid thin #ffc125;
background-color:#ffc125;
}

Missing Open Tag as Valid

If you have a page without a opening body tag, but does have a closing one, W3C HTML validation report it as valid.

it's technically valid because body tag is optional, but very annoying broken syntax.

In XML ideal, this means the code is not well-formed.

Here's the sampe html:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>W3C HTML Validation Problem: Mismatch Tag</title>
</head>

<h1>W3C HTML Validation Problem: Mismatch Tag</h1>

<p>This is a test page.</p>

<p>This is a html4 strict page. This page doesn't have a opening “body”
tag, but has a closing one.</p>

</body>
</html>

XHTML Style br Tag with Slash as Valid HTML 4

If you use the XHTML style tag such as br with a slash <br />, that is, a Self-Closing Tag with a slash, it's reported as valid. W3C only gives a warning. However, this is technically invalid in HTML 4.

Test page:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>W3C HTML Validation Problem: Slash End Tag</title>
</head>
<body>

<h1>W3C HTML Validation Problem: Slash End Tag</h1>

<p>This is a test page.
This page is html 4.01 strict.
</p>

<p>This page contains a
<br />
“br” tag with a slash.</p>

</body></html>

HTML validation