I totally agree with @jgaiser. What I've learned about KF8 while creating my own books is that the Kindle Previewer will create them in some cases even with errors. That is, the Kindle Previewer tells you that certain errors occurred during the compiling process, yet if the errors were not catastrophic it will still create the book. I also learned through trial and error that KF8 books compiled with Kindle Previewer that have errors will often not display correctly. If you get an error-free compiled book then the display issues go away. Amazon is forcing us to use good clean code (HTML5, CSS3, content.opf, and toc.ncx). A lot of folks have gotten used to using sloppy code and getting a book that displays correctly, but with KF8 you better get it right or it won't display right. Whose fault is that? Certainly not the device firmware. It is the creator/author's fault for being sloppy. Programmers know that code should be as clean as possible so ugly things don't happen during compile. KF8 book creators need to learn this too.