Personally, I very much dislike using CSS classes unless required. I prefer having a clean markup with classes used only where they make sense. For a context,

Personally, I very much dislike using CSS classes unless required. I prefer having a clean markup with classes used only where they make sense. For a context, I somehow can't wrap my head around writing something like: <div class="nav nav-inverse nav-hide-xs"> when `<nav>` makes more sense. Sure, if you have a case with alternate "inverse" navbar, go ahead with a class `<nav class="inverse">`. About the flexbox, ah, well, even now they have undefined behaviour on several elements such as a `fieldset` [1]. [1]: http://stackoverflow.com/questions/28078681/why-cant-fieldset-be-flex-containers http://stackoverflow.com/questions/28078681/why-cant-fieldse...