Back to Error DirectoryW3C EPUBCheck Standard
CSS-029Retailer Warning

Found CSS class name "resource" but no "resource" property was decl...

Found CSS class name "resource" but no "resource" property was declared in the package document.

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Fix all CSS-029 errors in your EPUB automatically

PreFlight checks for CSS-029 issues in memory and provides 1-click remediation during client-side packaging.

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What This Error Means in Plain English

EPUBCheck detected Found CSS class name "resource" but no "resource" property was declared in the package document.. Digital reading systems and bookstores require standard conformance to ensure compatibility across all reading apps.

Why Retailers & EAA Regulations Block This File

Automated book distributors (Apple Books, Amazon KDP, Kobo, and IngramSpark) run strict EPUBCheck validation on ingest and reject non-compliant files.

Technical Specification: W3C EPUBCheck rule CSS-029: Found CSS class name "resource" but no "resource" property was declared in the package document.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule CSS-029 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the CSS-029 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.