如下图效果：
<!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<head>
<title>MOSS</title>
<style>
body {
background-color: #fff;
color: #222;
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
height: 100vh;
margin: 0;
}
img {
max-width: 100%;
max-height: 50px;
}
h1 {
margin-top: 40px;
}
</style>
</head>
<body>
<img src="logo.png" alt="Logo" />
<h1>为保证用户体验，MOSS 需要进行升级，现已停止服务</h1>
</body>
</html>
