CENTER ALIGN THE BUTTON VERTICALLY AND HORIZONTALLY
Run 
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>HTML</title>
<style>
    .container {
	  height: 200px;
	  position: relative;
	  border: 3px solid green
	}
	 .center {
	  margin: 0;
	  position: absolute;
	  top: 50%;
	  left: 50%;
	  -ms-transform: translate(-50%, -50%);
	  transform: translate(-50%, -50%);
    }
	button {
	  font-size: 20px;
	  background: blue;
	}
</style>
</head>
<body>
   <h2 style="text-align:center">Center align the button horizontally and vertically </h2>
   <div class="container">
     <div class="center">
       <button>centered button </button>
	 </div>
   </div>

</body>
</html>