Updated 03-Aug-2025
In the attempt to remove as much of javascript as possible, certainly not relying on jquery and its ilk, we need a CSS-only sticky header and/or footer.
This is normally quite straightforward. However, the trick comes when logged into WordPress and the Adminbar is present.
If only the #mobile-header, .site-header, #site-navigation, or #masthead is needed for sticky, then voila: