CSS 弹层效果
参考：https://segmentfault.com/a/1190000006108996
当前页面div半透明遮罩效果：
.div-hide{
filter:alpha(Opacity=80);-moz-opacity:0.5;opacity: 0.5;
}
弹出层div居中对齐：
.pop-div{
display: none;
margin: auto;
top: 50%;
left: 50%;
-webkit-transform: translate(-50%, -50%);
-ms-transform: translate(-50%, -50%);
transform: translate(-50%, -50%);
font-size: 1.1rem;
line-height: 1.1rem;
color: #16c5ab;
background-image: url(<%=basePath%>/static/images/visit/pop-bg.png);
background-size: 100% 100%;
height: 8rem;
width: 18rem;
position: absolute;
}