<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
#wrapper {
width: 100%;
height: 300px;
border: 2px solid #000;
display: flex;
align-items: center;
justify-content: center;
}
button {
height: 30px;
width: 90px;
}
</style>
</head>
<body>
<div id="wrapper">
<button type="button">W3Docs</button>
</div>
</body>
</html>