Originally Posted by Doitsu
Some of the warnings are caused by the fact that MOBI/KF8 files do not support all ePub tags, I.e. you'll have to live with them.
The errors are most likely caused by syntax errors in the source ePub that you didn't notice because Calibre will convert source files with serious errors in them without letting you know.
You may want to check the ePub for errors by clicking the big green checkmark button in Sigil to run Flightcrew and
check the file with ePubCheck Online
You also my want to check the stylesheet for errors by selecting the Validate with W3C option in Sigil.
Once again, thank you. I used the Sigil Flightcrew validator, as suggested, and threw up some errors, which weren't picked up by Sigil's own HTML checks??, by editing the content.opf I was able to fix these and, voila, KindleGen worked!
I do use the online ePubCheck, but this particular file is 18 megs (they have a 10 meg max), I got mixed up with another title I'm working on. I've tried to do this locally but get the java.lang.NoClassDefFoundError and I'm simply not good enough to figure out JavaClassloaders. I'll post this as a separate question.
It did, however, throw up another puzzle and I have attached the screenshot. The validation process didn't like the external "a href" links to websites. I know they work since I checked them. Luckily, this didn't affect the Kindle book which looks much better now with lines spaces in situ.
Great! Job done