自适应背景图片

<div id="Layer1" style="position:absolute; width:100%; height:100%; z-index:-1">    
<img src="pictures/background.jpg" height="100%" width="100%"/>    
</div> 




.background-pic{
    background: url(../images/login/background.jpg) no-repeat center center;
    background-size:cover;
    background-attachment: fixed;
    width: 100%;
    height: 100%;
    position: fixed;
    top:0;
    left:0;
    right:0;
    bottom:0;
}


<div class="background-pic"></div>