When I just grab any ebook, I might see in certain files:
Code:
toc.ncx --> xml:lang="en-US"
content.opf --> <dc:language>en</dc:language>
nav.xhtml --> xml:lang="en"
*.xhtml --> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xml:lang="en">
I have always wondered which language setting is really used and which ones are superfluous?