Footnotes in epub

I tried a book with a fottnote to compile into epub and got this error message from D2D’s validator:

.tmp.tmpbdqmelkg.epub/OPS.content.opf(14,18): Error while parsing file: character content of element “dc:description” invalid; must be a string with length at least 1 (actual length was 0)

Kobo’s validator told me the same thing.

What does this even mean? And how do I avoid that?

Check the Compile > Meta Data view > Description field. Most likely you have some invisible space inside the “Description” editor view, which is causing the problem. If not, please upload a demo project which shows the problem. Thanks!

that was it.
I was looking at a completely different place. Because this I could not imagine.
I was just looking for what is different with this book compared to the other one .

thanks … I’m slowly getting forward.

Abnd thanks for your patience.