When I error check my Pages-created epub, I get the error code "undeclared prefix: ibooks." How do I resolve this error?

Question

I'm creating an epub with Pages for upload to various sites. When I error check the epub, I get only one error message: "undeclared prefix: ibooks." The file itself works perfectly and looks fantastic when I open it directly from my computer/ipad with numerous Mac-compatible reading apps. However, I have no idea what distortions this "error" will cause when the epub is uploaded and redistributed. Has anyone else had this problem? If so, did it create problems in distribution? Or is it irrelevant? Thanks for any practical and straight forward answers and/or suggestions.

Answer 1

Based on that, it does sound like the sites you were having problems with had to do with filenames, not this error.  I can imagine a site running a standard EPUB verifier, and if any errors at all are thrown rejecting the file, but practically speaking an unknown META tag (what's causing this error) should be ignored by the parser and therefore by definition be harmless.
I was using a free Java-based checker myself, and the fact that I managed to clear up the error indicates to me (unless I'm remembering wrong or misunderstood what fixed it in my case) that it's probably not technically the EPUB checker's failure to recognize the Apple META property; more accurately, it's that the XML dictionary the file is referencing doesn't include the Apple items in it, so the EPUB checker is correctly complaining about it.
It could also be something as simple as Pages generating a file that is marked as an EPUB v2 file but that uses EPUB v3 features (I know my book was intended to be v3, and I could have inadvertently used headers for v2).
Regardless, if the sites accept it, there's a good chance it is okay; DRM, at least, isn't going to change anything--only if an e-reader changes its EPUB parser at some point and breaks something, which seems unlikely.
However, the best way to find out if it's going to work right is to test it.  Kindle is far and away the most popular reader, so try it with that and see if it comes out looking how you expect.  You should be able to view it in the Kindle application, and there is also a Kindle simulatior available from Amazon that lets you see how an e-paper Kindle will render books without having to buy one.  They have very limited EPUB support as far as features go, so it's definitely worth testing even if there are no errors--a lot of things iBooks will display just fine a Kindle will choke on.  The older e-paper Nooks, in my experience, are even worse.