d-tw-none css code example

Example 1: bootstrap display none

<!-- Bootstrap 4 -->
<div class="d-none"></div>

<!-- Bootstrap 3 -->
<!-- <div class="hidden-{screen size}"></div> -->
<div class="hidden-md"></div>

Example 2: is display-block a class

<span class="d-block p-2 bg-primary text-white">d-block</span>
<span class="d-block p-2 bg-dark text-white">d-block</span>