If the epub came from calibre conversion there'll probably be something like this for chapter headers in the xhtml files:
Code:
<h2 id="calibre_toc_3" class="calibre5">Chapter Two </h2>
And in the stylesheet.css there'll probably be something like this
Code:
.calibre5 {
display: block;
font-size: 1.375em;
font-weight: bold;
line-height: 1.2;
margin-bottom: 0.83em;
margin-left: 0;
margin-right: 0;
margin-top: 0.83em
}
If you add the
text-align centre into the calibre5 definition then everything that uses calibre5 will be centred.
Because the epub came from calibre conversion there's a good chance chapter headings will be the only things that will use that particular css class - use Search make sure that's true. It won't necessarily be 'calibre5' could be 'calibre101'
BR