In the editor, CSS live computed final styles was showing that margins were 0, but the file preview panel had clear greater than 0 left and right margins. I saw there was a second css file that had
Code:
@page {
margin-left: 2em;
margin-right: 2em;
}
and fixing that made the margins visibly zero.
Why weren't the 2em left and right margins reflected is the editor's live CSS panel?