Originally Posted by wallcraft
Some e-books are MOBI only, and it is probably a good thing that most of these are hidden by DRM because MobiPocket has quite a few non-standard extensions to HTML which are likely used liberally in such e-books.
Actually almost all eBook formats as non-standard to html constructs since HTML is a scroll based format while eBooks are page based. Standard HTML has no notion of pages, headers, footers, footnotes etc. which are the staples of books. This is why there are explicit eBooks standards being developed and things called XHTML.