ERROR ITMS-9000: ... could not parse OPS/content1.xhtml: duplicate id: viewport-popup-0-aside" at Book (MZItmspBookPackage)
ERROR ITMS-9000: "IAM_eBook1.ibooks: could not parse OPS/content1.xhtml: duplicate id: viewport-popup-0-aside" at Book (MZItmspBookPackage) says the error message and I am desperately looking for help.
MacBook Pro (15-inch Core 2 Duo), OS X Mavericks (10.9.2)