If you have uploaded any online URLs that we don't recognise, we will show those as errors in the book at the bottom of the left hand menu options.
The likely cause is where a URL has been added which contains spaces in the address (eg www. website.co.uk). We treat each space as a new URL, so you may see the address broken up in the errors list. You'll be able to either amend the address to the right URL and click on Update, or bin all the errors and upload the URL again to your book.
If you have any questions on this please get in touch.