Any validation errors, please post them here, that would be very helpful.
Browsers parse and use custom tags just fine, regardless of what a validator says. The <j> tag is a special element that creates an “enjambment”, i.e. it splits a long line of verse over two lines, like this.
But yeah if Google Play doesn’t like it we should fix it. It’s not really relevant in ereaders anyway (because the reading environment is arbitrary) so we should probably just strip them from there.
