html, body {
display: block;
height: 100%;
position: relative;
}
body {
margin: 0;
overflow: auto;
}
.main {
width: 100%;
}
.overlay {
background: rgba(0, 0, 0, .5);
bottom: 0;
box-sizing: border-box;
display: none;
height: 100%;
left: 0;
outline: none;
overflow: auto;
position: absolute;
right: 0;
top: 0;
}
.dialog {
background: #fff;
margin: 20px auto;
padding: 20px;
position: relative;
width: 640px;
}