#overlay3{
    display: none;
    position: fixed;
    top:0; right:0; bottom:0; left:0;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1000;
}
#overlay3:target{
    display: block;
}
.popup_block{
    background: #fff;
    padding: 20px;
    border: 10px solid #ddd;
    position: relative;
    margin: 10% auto;
    width: 40%;
    box-shadow: 0px 0px 5px #000;
    border-radius: 5px;
}
img.btn_close {
    float: right;
    margin: -55px -55px 0 0;
}