# EPUBCheck CSS-030: overlay styles without CSS, how to fix it

Source: https://epubcc.com/epubcheck/css-030/ (updated 2026-11-04)

EPUBCheck CSS-030 is an error message: “The package document declares media overlays styling class names but no CSS was found in the content document.” The package declares media overlay styling class names, but a chapter with narration has no CSS. EPUB requires every content document with a media overlay to include a stylesheet, linked or embedded, that defines those classes, otherwise the text being read is not highlighted as intended.

- Official message (EPUBCheck 5.4.0): The package document declares media overlays styling class names but no CSS was found in the content document.
- Default severity: Error

## Typical causes

- A chapter with narration that does not link the stylesheet the other chapters use.
- media:active-class declared in the package while the class is defined nowhere.

## How to fix it

1. Link the stylesheet that defines the classes from the chapter EPUBCheck names, for example <link rel="stylesheet" href="styles.css" type="text/css"/>.
2. Make sure the stylesheet really defines the class declared in media:active-class (and media:playback-active-class, if used).
3. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the CSS defines the class but the package does not declare it, the message is CSS-029.

## 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.