BTW, if you select
Create HTML Table Of Contents, Sigil will automatically add the proper semantics. If you select the HTML TOC and select Add Semantics... > Table of Contents, it'll remove the TOC semantics.
You can check the semantics in your book by looking at the
<guide> section in
content.opf, which should look like this:
Code:
<guide>
<reference type="toc" title="Table of Contents" href="Text/TOC.xhtml"/>
<reference type="text" title="Text" href="Text/chapter1.xhtml"/>
</guide>
(Of course your file names will differ.)