An element is a building block of HTML that determines structure. Elements are indicated by angle brackets (< >) and consist of a start and an end tag. For example, a paragraph is defined by the start tag <p> and end tag </p>.
If there are issues with your elements, you might see these errors.
ERROR ITMS-9000: Unknown element
The unknown element error indicates that you're using an HTML element that isn't allowed. Not all HTML elements are supported in XHTML. For example, <font> isn't allowed. Use CSS instead of HTML to add style to your book.
ERROR ITMS-9000: Element not allowed
Some elements that are normally allowed aren't allowed in certain contexts. Go to the iBooks Asset Guide in the Resources and Help section of iTunes Connect to see the correct context of allowed elements, such as <img> and <a>.
ERROR ITMS-9000: Unfinished element
The unfinished element error indicates that your ePub file has one of these issues:
- An XHTML element doesn't have a closing tag.
- An XHTML element has an incorrect closing tag.
Make sure that all of your closing tags are in the correct format, such as </div>.