CSS 背景图片铺满浏览器，拖动、上下拉背景图片不出界，下面分享下CSS：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>CSS 背景图片铺满浏览器，任何情况下都铺面整个浏览器</title>
</head>
<body>
<style>
body {
margin: 0;
padding: 0;
height: 100%;
width: 100%;
background-image: url(test.jpg);
background-repeat: no-repeat;
background-size: cover;
}
.login {
height: 300px;
width: 400px;
border: 1px solid #f00;
position: absolute;
left: 50%;
top: 50%;
margin: -150px 0 0 -200px;
}
</style>
<div class="login"></div><!----红色框---->
</body>
</html>