Nice work!
Some random nitpicks:
- The R in MobileRead should be capitalised
- The N at the start of Notepad should be capitalised
- If you are trying to teach as little HTML as possible (if you know what I mean!) why are you bothering to include those two meta tags? You'd be better off teaching the Doctype tag - it's scary, but important. The other important tag for a HTML page is the title tag. Although it's not needed in an epub, it is in every other HTML page. That one comes down to a judgement call, I guess...
- Absolute newbies may not know directory=folder
- The em explaination is a bit confusing... but it is hard to explain!
- "An ePub document is compressed file" think you mean "An ePub document is a compressed file"
- "It is not necessary to create a TOC inside the book" this is a bit confusing. Maybe "It is not necessary to create a HTML file with an additional TOC inside the book..."
- "link from body to note and back" Newbies may not know what you mean by "link" as they haven't learned about anchors/hyperlinks.
Again, it's really, really good! I know how hard it is to try and create a teaching document. Well done!