<div class="container">
  <p>Play with the values of the border radius to see how the corner curvature changes.</p>
  <div class="element element-1">I have a circular bottom left corner</div>
  <div class="element element-2">I have an elliptical bottom left corner</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;
  background-color: #0099cc;
  color: white;
  margin: 30px;
  width: 200px;
  height: 200px;
  padding: 30px;
  float: left;
}

.element-1 {
  border-bottom-left-radius: 50px;
}

.element-2 {
  border-bottom-left-radius: 100px 50px;
}