The definition of the footer element  makes clear that it belongs to "its nearest ancestor sectioning content or sectioning root element".
For the header element  such a clarification is missing:
> The header element represents a group of introductory or navigational aids.
However, in the Note it refers to sections:
> A header element is intended to usually contain the section's heading […]
Is this difference intended?
I thought that footer and header would differ only in what *kind* of content they should be used for.
Refer to resolution of https://www.w3.org/Bugs/Public/show_bug.cgi?id=20550
*** This bug has been marked as a duplicate of bug 20550 ***