[odedta]

For some meta tags such as:

<meta property="ibooks:iphone-orientation-lock">none</meta>
<meta property="ibooks:ipad-orientation-lock">none</meta>

You must include the ibooks prefix

prefix="ibooks: http://vocabulary.itunes.apple.com/rdf/ibooks/vocabulary-extensions-1.0/"

in the package so your file will pass validation, if it works with or without the prefix I have no clue and I don't intend to try, just stick with the ePub standard and you should be fine.

If you are working with Fixed-Layout ePubs you will have to use the meta tags:

<meta property="rendition:layout">pre-paginated</meta>
<meta property="rendition:orientation">portrait</meta>
<meta property="rendition:spread">landscape</meta>

AND include the prefix:

prefix="rendition: http://www.idpf.org/vocab/rendition/#"

to the package.opf

Now, if you have both fixed layout and embedded fonts the correct form of declaring the package prefixes are as follows:

prefix="rendition: http://www.idpf.org/vocab/rendition/# ibooks: http://vocabulary.itunes.apple.com/rdf/ibooks/vocabulary-extensions-1.0/"

Meaning, just add a space between them.

Everything I said so far is ePub 3 standards requirements. In order to be backwards compatible, meaning, conforming to ePub 2 standards you must include the com.apple.ibooks.display-options.xml file in order to have embedded fonts or fixed layout.

Here is a template I use:

<?xml version="1.0" encoding="UTF-8"?>
<display_options>
	<platform name="*">	 <!-- all devices -->
		<option name="fixed-layout">true</option> <!-- fixes the layout -->
		<option name="specified-fonts">false</option>	 <!-- set to "true" when embedding fonts -->
		<option name="open-to-spread">true</option>	 <!-- single page or full spread on open -->
		<!--<option name="orientation-lock">landscape-only</option>	 "landscape-only" or "portrait-only" or leave this line commented -->
		<option name="interactive">false</option>	 <!-- set to "true" when using javascript or canvas -->
	</platform>
</display_options>

To summarize, in my opinion, it's best to include both the tags you need and the com.apple.ibooks.display-options.xml file to have backwards compatibility, now, we also want our files to be validated to know they are well-formed, so we declare the prefixes we used in the package tags.