<div class="container">
  <div class="el">
    I'm an ordinary div, with standard div styling.
  </div>
  <div class="el unset">
    I have had my CSS properties unset.
  </div>
  <div class="el">
    I'm an ordinary div, with standard div styling.
  </div>
  <div class="el">
    I'm an ordinary div, with standard div styling.
  </div>
</div>

body {
  background-color: #F5F5F5;
  color: #555;
  font-size: 1.1em;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.container {
  margin: 40px auto;
  max-width: 700px;
}

.el {
  background-color: #C0C0C0;
  color: #006400;
  font-family: Georgia, Times, Times New Roman, serif;
  padding: 1em;
  margin: 1em;
}

.el.unset {
  all: unset;
}