These declarations serve to provide a consistent set of classes to be able to apply CSS overrides for older IE browsers. While we are not using them specifically as the moment, we may take advantage as we do more extensive browser testing. Similarly for no-js class - a standard way to apply styling for anything no-js related. This comes from https://github.com/h5bp/html5-boilerplate/blob/v4.3.0/doc/html.md#conditional-html-classes but is not strictly necessary to have.