It's a good guide, but I'm not sure I understand the point of a site-specific JavaScript toggle to override the browser's default theme. The only thing that immediately comes to mind is to override a browser default of 'light' for a multimedia experience, as a dark background is conventionally used for these in order to give more emphasis to the multimedia content (or perhaps as an anachronism from the use of projectors). Any other examples where this kind of toggle would be useful?
