EpubCheck is an invaluable tool for assessing the quality of EPUB files. Still, it is possible that EPUBs that are valid according to the format specification (and thus EpubCheck) are nevertheless inaccessible to some users. Some weeks ago a colleague sent me an EPUB 2 file that produced some really strange behaviour across a number of viewer applications. For a start, the text wouldn’t reflow properly after re-sizing the viewer window, and increasing the font size resulted in garbled text. Running the file through EpubCheck did return some validation errors, but none of these were related to the behaviour I was getting. Closer inspection revealed some very peculiar stylesheet and HTML use.

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