[orange!]

This isn't really a Sigil question--if there's a better place to ask generic CSS questions, please let me know.

The book I'm working on uses a short horizontal line to separate sections within a chapter. So my inclination was to use this in my html:

<hr class="sep" />

and this in my stylesheet:

hr.sep
{
width: 72px;
text-align: center;
}

Looks fine in Book Preview, but on the device, the <hr> is left-aligned.

My question: is there an industry-standard way to render a section separator like this?

Thanks in advance!