//邀朋友来抽签的图片样式控制
.cover { background: url(share.png) top right no-repeat; background-size: 50%; background-color: rgba(0, 0, 0, 0.7); position: fixed; width: 100%; height: 100%; top: 0; left: 0; }
body { background: url(bg.jpg) no-repeat #E8DFD0; background-size: cover; }
原文：http://www.cnblogs.com/zxyun/p/5286303.html