<div class="container">
  <p>Change the values of the <code>border-top</code> property to see how the top border changes.</p>
  <div class="element">
    <p>
      I have a 5px solid green top border.
    </p>
  </div>
</div>
body {
  background-color: #F5F5F5;
  color: #555;
  font-size: 1.1em;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.container {
  margin: 40px auto 0;
  width: 90%;
}

.element {
  padding: 20px;
  height: 200px;
  background-color: white;
  border-top: 5px solid #009966;
}