Try it Editor

<!DOCTYPE html>
<html>
<head>
<style>
div {
  width:400px;
  margin: auto;
  border: 1px solid green;
}
</style>
</head>
<body>
 
<h2>Use of margin:auto</h2>
<p>You can set the margin property to auto to horizontally center the element within its container. The element will then take up the specified width, and the remaining space will be split equally between the left and right margins:</p>
 
<div>
This div will be horizontally centered because it has margin: auto;
</div>
 
</body>
</html>