Personally, I recommend using a full path (back) everywhere. If the section gets split, the path gets adjusted. If it is only a current page, relative path (starts with #) it will orphan.
Here is a sample(borrowed from a TOC, but it still applies)
Code:
<p class="indent">Per regulation <a href="../Text/footnotes.html#fn1-01" id="chap1">[*1-01]</a> and others. </p>
Link back to the Anchor point
Code:
<p class="foot"><a class="calibre4" href="../Text/chap1.xhtml#chap1">ONE</a></p>