<span class="border"></span>
<span class="border border-0"></span>
<span class="border border-top-0"></span>
<span class="border border-right-0"></span>
<span class="border border-bottom-0"></span>
<span class="border border-left-0"></span>

<span class="border border-primary"></span>
<span class="border border-secondary"></span>
<span class="border border-success"></span>
<span class="border border-danger"></span>
<span class="border border-warning"></span>
<span class="border border-info"></span>
<span class="border border-light"></span>
<span class="border border-dark"></span>
<span class="border border-white"></span>

<span class="rounded"></span>
<span class="rounded-top"></span>
<span class="rounded-right"></span>
<span class="rounded-bottom"></span>
<span class="rounded-left"></span>
<span class="rounded-circle"></span>
<span class="rounded-0"></span>

<div class="clearfix">
  <span class="float-left">Float left</span>
  <span class="float-right">Float right</span>
</div>

<div class="float-sm-right">Float right on small screens or wider</div><br>
<div class="float-md-right">Float right on medium screens or wider</div><br>
<div class="float-lg-right">Float right on large screens or wider</div><br>
<div class="float-xl-right">Float right on extra large screens or wider</div><br>
<div class="float-none">Float none</div>

<div class="mx-auto bg-warning" style="width:150px">Centered</div>

<div class="w-25 bg-warning">Width 25%</div>
<div class="w-50 bg-warning">Width 50%</div>
<div class="w-75 bg-warning">Width 75%</div>
<div class="w-100 bg-warning">Width 100%</div>
<div class="mw-100 bg-warning">Max Width 100%</div>

<div style="height:200px;background-color:#ddd">
  <div class="h-25 bg-warning">Height 25%</div>
  <div class="h-50 bg-warning">Height 50%</div>
  <div class="h-75 bg-warning">Height 75%</div>
  <div class="h-100 bg-warning">Height 100%</div>
  <div class="mh-100 bg-warning" style="height:500px">Max Height 100%</div>
</div>

<span class="align-baseline"<baseline</span<
<span class="align-top"<top</span<
<span class="align-middle"<middle</span<
<span class="align-bottom"<bottom</span<
<span class="align-text-top"<text-top</span<
<span class="align-text-bottom"<text-bottom</span<

 <nav class="navbar navbar-expand-sm bg-dark navbar-dark fixed-top">
  ...
</nav> 

 <nav class="navbar navbar-expand-sm bg-dark navbar-dark fixed-bottom">
  ...
</nav>