HTML Validation

HTTP resource not retrievable. The HTTP status from the remote server was: 429.

About This HTML Issue

The “HTTP resource not retrievable” error with an HTTP status code of 429 indicates that the W3C Validator was temporarily blocked from accessing a specific URL because the remote server is rate-limiting incoming requests. This typically happens when too many requests are made in a short period of time.

To resolve this:

Try checking the site at a lower speed, or less often.
If you’re the server owner, check your server or CDN settings for rate-limiting rules that might be too aggressive.

This error is usually temporary. Waiting before retrying can often resolve the issue.

Learn more:

→ MDN: 429 Too Many Requests

Last reviewed: July 21, 2025

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Related W3C Validator Issues

Attribute “isolang” not allowed on element “html” at this point.

Instead of using the isolang attribute to define the language of the document, you can use lang with an ISO 639-1 two character code.

For example, for Portuguese:

<html lang="pt">

Bad value X for attribute “multiple” on element “input”.

Invalid value used for the multiple attribute on an input element.

The multiple attribute is a boolean attribute for certain input types (e.g., email, file). Boolean attributes must appear without a value (or with the same name as value in legacy cases), and they only work on specific types. Valid usage: <input type="email" multiple> or <input type="file" multiple>. Invalid usage includes multiple="1", multiple="true", or using multiple on unsupported types like text or number. The email type allows comma-separated addresses when multiple is present; the file type allows selecting more than one file.

HTML Examples

Example that reproduces the error

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Invalid multiple</title>
</head>
<body>
<!-- Invalid: value on boolean attribute, and wrong type -->

  <input type="text" name="tags" multiple="1">
</body>
</html>

Corrected example

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Valid multiple</title>
</head>
<body>
<!-- Valid: boolean attribute without a value on supported types -->

  <input type="email" name="recipients" multiple placeholder="name@example.com, other@example.com">

  <input type="file" name="attachments" multiple>
</body>
</html>

HTTP resource not retrievable. The HTTP status from the remote server was: 404.

Stray start tag “html”.

The “version” attribute on the “html” element is obsolete. You can safely omit it.

In HTML5, there’s no need to specify the version attribute - it is now obsolete. Here’s an example minimal HTML document to start with:

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Test</title>
  </head>
  <body>
    <p></p>
  </body>
</html>

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