#img_modal {
 display: none;
 position: fixed;
 top: 0;
 left: 0;
 width: 100%;
 max-width: 100%;
 height: 100%;
 background: rgba(0,0,0,0.3);
 z-index: 100;
}
#img_modal img {
 position: absolute;
 top: 0;
 bottom: 0;
 left: 0;
 right: 0;
 margin: auto;
 max-width: 95%;
 max-height: 95%;
}