<div class="container">
  <p></p>
  <div class="element"></div>
</div>
body {
  background-color: #F5F5F5;
  color: #555;
  font-size: 1.1em;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.container {
  margin: 50px auto;
  max-width: 700px;
}

.element {
  max-width: 500px;
  height: 250px;
  border: 1px solid black;
  margin: 0 auto;
  background-image: linear-gradient(to bottom right, yellow, deeppink, #006699);
}