# EPUBCheck CSS-001: forbidden CSS property, how to fix it

Source: https://epubcc.com/epubcheck/css-001/ (updated 2026-11-04)

EPUBCheck CSS-001 is an error message: “The "…" property must not be included in an EPUB Style Sheet.” The stylesheet uses a property that EPUB does not allow in its style sheets. EPUB 3.3 forbids direction and unicode-bidi in CSS, because reading apps may switch CSS off and the text direction would then be lost; EPUBCheck names the property.

- Official message (EPUBCheck 5.4.0): The "%1$s" property must not be included in an EPUB Style Sheet.
- Default severity: Error

## Typical causes

- CSS copied from the web that sets text direction in the stylesheet.
- Right-to-left books (Arabic, Hebrew) where the direction was put in CSS instead of the markup.

## How to fix it

1. Open the file EPUBCheck names (the message gives the path, line and column) in a text or EPUB editor such as Sigil, or unzip the EPUB and open it there.
2. Remove the direction or unicode-bidi declaration from the stylesheet.
3. Set text direction with the dir attribute in the XHTML instead, for example <html dir="rtl"> or <p dir="ltr">, and use bdo for bidirectional overrides.
4. For right-to-left page turning, set page-progression-direction on the spine.
5. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the CSS cannot be parsed at all, the message is CSS-008.

## Sources

- EPUB 3.3, §6.3.1.2 CSS requirements: https://www.w3.org/TR/epub-33/#sec-css-req (read 2026-11-04)

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