.dark {
background: rgba(0,0,0,.5);
width: 100%;
min-height: 100%;
position: fixed;
top: 0;
left: 0;
display: none;
z-index: 999;
}

.banner {
display: block;
margin: 0 auto;
width: 810px;
height: auto;
max-width: 100%;
top: 100px;
position: relative;
}

.banner_image {
max-width: 100%;
width: auto;
margin: 0 auto;
z-index: 100;
border: 5px solid #000;
padding: 0;
}

.banner_close {
color: #fff;
background-color: #000;
position: absolute;
top: 0;
right: 0;
padding: 10px;
cursor: pointer;
}

.banner_close:before {
content: 'X';
}