css 背景图片自适应

body{
height:100%;
overflow:hidden;
}
.bg {
background-image: url(../../img/beijing.jpg);
width:100%;
height:100%;
background-size:100% 100%;
position:absolute;
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='bg-login.png',sizingMethod='scale');
}

</body>