Bad value “text/html; charset=iso-8859-1” for attribute “content” on element “meta”: “charset=” must be followed by “utf-8”.

A meta element with http-equiv="Content-Type" must declare charset=utf-8 in its content attribute, so text/html; charset=iso-8859-1 is rejected.

The HTML living standard allows a single character encoding for HTML documents: UTF-8. When you declare it with the http-equiv form, the content attribute must be text/html; charset=utf-8 (case-insensitive). Any other value after charset=, including ISO-8859-1 (also known as Latin-1), fails validation.

ISO-8859-1 is a legacy single-byte encoding for Western European languages. Browsers don't decode it as declared anyway: the WHATWG Encoding Standard maps the iso-8859-1 label to windows-1252, so a page labelled ISO-8859-1 is read as Windows-1252. UTF-8 covers every character in both, plus the rest of Unicode.

Changing the declaration is only half the fix. Save the file itself as UTF-8 too, or accented characters such as é or ñ, stored as single bytes in a Latin-1 file, show up as replacement characters (�). If your server sends a Content-Type header with charset=iso-8859-1, update it as well, because the HTTP header takes precedence over the meta element. When the file is already UTF-8, the validator also reports that the internal encoding declaration disagrees with the actual encoding; correcting the meta element clears both errors.

The shorter <meta charset="utf-8"> does the same job and is the preferred form. Keep it within the first 1024 bytes of the document, usually as the first child of head.

Invalid example

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
  <title>Café menu</title>
</head>

Valid example

<head>
  <meta charset="utf-8">
  <title>Café menu</title>
</head>

Learn more:

MDN Reference

HTML meta element - MDN

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MDN Reference

The http-equiv attribute - MDN

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WHATWG Spec

Encoding Standard - WHATWG

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