In some HTML elements, attribute names need to be case-sensitive to take effect, for example, the viewBox attribute within the <svg> element.

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Based on the recent development of the EPUB format in recent years, more and more people are using SVG for image layout in XHTML. Currently, when using SVG, attributes within the viewBox are converted to lowercase, and during testing in Apple Books or Chrome Browser, it was found that <svg viewbox="0 0 960 1080"> is ineffective until it is adjusted to <svg viewBox="0 0 960 1080">.

Upon investigation, it was found that the issue originates from the Python lxml package. After processing with html.document_fromstring, the attributes are converted to lowercase. While this aligns with XML conventions, it is not suitable for HTML5.