outline

outline: solid;

outline: dashed red;

outline: 1rem solid;

outline: thick double #32a1ce;

outline: 8px ridge rgba(170, 50, 220, 0.6);
border-radius: 2rem;

<section class="default-example" id="default-example">
  <div class="transition-all" id="example-element">
    This is a box with an outline around it.
  </div>
</section>

#example-element {
  padding: 0.75rem;
  width: 80%;
  height: 100px;
}

/* style */
outline: solid;

/* color | style */
outline: #f66 dashed;

/* style | width */
outline: inset thick;

/* color | style | width */
outline: green solid 3px;

/*   */
outline: inherit;
outline: initial;
outline: unset;

<a href="#">This link has a special focus style.</a>

a {
  border: 1px solid;
  border-radius: 3px;
  display: inline-block;
  margin: 10px;
  padding: 5px;
}

a:focus {
  outline: 4px dotted #e73;
  outline-offset: 4px;
  background: #ffa;
}