<!DOCTYPE html>
<!--
 | Setting the border radius for background color.
 |   https://www.w3.org/TR/css3-background/#border-radius
 -->
<html>
<head>
  <style>
    div {
      border-radius: 25px;
      background-color: #ff6363;
      height: 100px;
      width: 100px;
    }
  </style>
</head>
<body>
  <div></div>
</body>
</html>