+>> ikiwiki always generates HTML5, since 3.20150107. The `html5` option has
+>> been repurposed to control whether we generate new-in-HTML5 semantic
+>> markup like `<section>` and `<nav>` (`html5` enabled), or HTML4 equivalents
+>> like `<div>` with a class (`html5` disabled). The default is still off,
+>> although I should probably either toggle it to on or remove the option
+>> altogether in the next release. --s
+