Ahh, that's a great idea!
I always thought
h tags with
id tags were semantically incorrect.
Off to try that

! Hope it works
I know this is the calibre forum, not the kindle one, but could I ask whether doing the whole <a id=""> thing is also a bad idea in MOBI formats? I do it all the time and have never thought that it was a road to errors? Now I'm second guessing my html work that I've done for mobi formats