css/css-sizing/div-auto-margin-ref.html - external/w3c/web-platform-tests - Git at Google

 <!DOCTYPE HTML>
 <title> Ensure element is centered by auto margin </title>
 <style>
   div {
     inset: 0;
     background-color: black;
     margin: auto;
     position: absolute;
     block-size: 200px;
     inline-size: 100px;
     border: 5px solid red;
   }
 </style>
 <div></div>
	<!DOCTYPE HTML>
	<title> Ensure element is centered by auto margin </title>
	<style>
	div {
	inset: 0;
	background-color: black;
	margin: auto;
	position: absolute;
	block-size: 200px;
	inline-size: 100px;
	border: 5px solid red;
	}
	</style>
	<div></div>