Pop up window - CSS

#mask {
    position:absolute;
    left:0;
    top:0;
    z-index:9000;
<!-- Background color -->
    background-color:#b4c9fd;
    display:none;
}
#boxes .window {
    position:absolute;
    left:0;
    top:0;
    width:440px;
    height:200px;
    display:none;
    z-index:9999999;
    padding:20px;
}
#boxes a {
<!--link color-->
    color:#d29dfe;
}
#boxes #dialog {
<!-- height and width of the box-->
    width:375px;
    height:225px;
    padding:20px;
<!-- background color of box-->
    background-color:#ffffff;
    text-align:center;
    border:1px solid black;
}
#boxes .close {
    padding:5px;
<!-- enter button background-->
    background:#bffbff;
<!-- enter button text color-->
    color:#000;
    border:1px solid black;
    margin:10px 10%;
}