HTML on Web pages is not PDF, so your description is a bit confusing in what you are really converting.
Next, Web pages are a SUPER SET of what is used for EPUB. Lots of things are not supported in EPUB (and many devices fail to fail gracefully

)
Last:
https://www.mobileread.com/forums/sh...d.php?t=118605
PDF is a terrible source to convert from. many devices use Adobe RMSDK. That can handle PDF natively (the image may not be large or moveable on small screens. But it shows up)