# CSS-029: undeclared overlay CSS class, how to fix it

Source: https://epubcc.com/epubcheck/css-029/ (updated 2026-11-04)

EPUBCheck CSS-029 is a usage message: “Found CSS class name "…" but no "…" property was declared in the package document.” The CSS uses a media overlay highlighting class name, but the package document does not declare the matching property. With media overlays, the class that highlights the text being read aloud must be declared in the package metadata (media:active-class or media:playback-active-class); EPUBCheck names both the class and the missing property.

- Official message (EPUBCheck 5.4.0): Found CSS class name "%1$s" but no "%2$s" property was declared in the package document.
- Default severity: Usage

## Typical causes

- A stylesheet copied from a book with narration into a package that never declared the class.
- The package metadata was edited and the media: meta elements were removed.

## How to fix it

1. Add the property to the package metadata, for example <meta property="media:active-class">my-active-item</meta>, with exactly one class name and no selector.
2. Or remove the unused class from the CSS if the book has no media overlays.
3. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the class is declared but no CSS reaches the chapter, the error is CSS-030.

## Sources

- EPUB 3.3, §9.3.4 Associating style information: https://www.w3.org/TR/epub-33/#sec-docs-assoc-style (read 2026-11-04)

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EpubCC.