css 背景图片铺满

body {
            width: 100%;
            height: 100%;
            background: url(img/loginbg.png);
            background-size: 100% 100%;
            background-repeat: no-repeat;
            background-position: center;
            background-attachment: fixed;
            background-size: cover;
            -webkit-background-size: cover;
            -moz-background-size: cover;
            -o-background-size: cover;
        }