While *sometimes* `no_js` was used for visitors without js (for example
disabling it on your browser) it was also used for some pages that were
disabled to JS capable browsers, including the 404 page.
Even worse, sometimes it was used on pages that *had* Javascript, such
as our `/activate-account` route. It has been renamed to `no_ember` to
indicate what it really is, a layout for the site that doesn't load our
Ember.js application.
