@papagelos,
Stop worrying. If you're struggling to understand what all these 'errors' may be, the chances are that they're not important enough to YOU to be called 'errors' -- or at least not yet
If you're new to ebooks, forget about 'errors'. If you have OCD tendencies they will gradually become obvious as you read more ebooks. If you get to the point where some little thing starts to really irritate you, just remember kiwidude's plugin. It might help you track down the rogue books so you can fix them. If you're a relaxed easygoing type you may never need it.