I'm still awaiting moderation for another post, but in the meantime I've tried tackling the errors as a group. Here's what I've found, plus a question:
I was getting errors because the html files were named html rather than xhtml. Consolidating the files (thanks, Calibre) made that a simple matter. So those are gone.
Next, I have many instances of this error:
Error while parsing file: element "h3" not allowed here; expected the element end-tag, text or element "a", "abbr", "area", "audio", "b", "bdi", "bdo", "br", "button", "canvas", "cite", "code", "command", "datalist", "del", "dfn", "em", "embed", "epub:switch", "i", "iframe", "img", "input", "ins", "kbd", "keygen", "label", "link", "map", "mark", "meta", "meter", "ns1:math", "ns2:svg", "object", "output", "progress", "q", "ruby", "s", "samp", "script", "select", "small", "span", "strong", "sub", "sup", "textarea", "time", "u", "var", "video" or "wbr" (with xmlns:ns1="http://www.w3.org/1998/Math/MathML" xmlns:ns2="http://www.w3.org/2000/svg")
In the code, I saw that Italic tags were outside the H3 tags like this:
Code:
<i>
<h3 id="sigil_toc_id_106">August 17, 1984 </h3>
</i>
Moving the Italic tags inside the H3 made the error disappear. I believe Sigil generated the code. That would see to be a pretty easy fix in the Sigil code, but it's going to be a chore doing it manually. But at least I know what it is.