demo.css

html, body {
	margin: 0;
	padding: 0;
	background-attachment: fixed;
	background-position: 50% 50%;
	background-size: cover;
}
a {
	text-decoration: underline;
}
a:hover {
	text-decoration: none;
}
.bg-red {
	background-image: url(../img/bg-red.jpg);
}
.bg-orange {
	background-image: url(../img/bg-orange.jpg);
}
.bg-yellow {
	background-image: url(../img/bg-yellow.jpg);
}
.bg-green {
	background-image: url(../img/bg-green.jpg);
}
.bg-cyan {
	background-image: url(../img/bg-cyan.jpg);
}
.bg-blue {
	background-image: url(../img/bg-blue.jpg);
}
.bg-purple {
	background-image: url(../img/bg-purple.jpg);
}
.bg-pink {
	background-image: url(../img/bg-pink.jpg);
}
.bg-black {
	background-image: url(../img/bg-black.jpg);
}
.body {
	max-width: 600px;
	margin: 0 auto;
	padding: 40px;
}
.body-s {
	max-width: 400px;
}
@media screen and (max-width: 600px) {
	.body {
		padding: 20px;
	}
}
.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    padding-top: 100px; /* Location of the box */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
}

/* Modal Content */
.modal-content {
    position: relative;
    background-color: #fefefe;
    margin: auto;
    padding: 0;
    border: 1px solid #888;
    width: 80%;
    box-shadow: 0 4px 8px 0 rgba(0,0,0,0.2),0 6px 20px 0 rgba(0,0,0,0.19);
    -webkit-animation-name: animatetop;
    -webkit-animation-duration: 0.4s;
    animation-name: animatetop;
    animation-duration: 0.4s
}

/* Add Animation */
@-webkit-keyframes animatetop {
    from {top:-300px; opacity:0}
    to {top:0; opacity:1}
}

@keyframes animatetop {
    from {top:-300px; opacity:0}
    to {top:0; opacity:1}
}

/* The Close Button */
.close {
    color: white;
    float: right;
    font-size: 28px;
    font-weight: bold;
}

.close:hover,
.close:focus {
    color: #000;
    text-decoration: none;
    cursor: pointer;
}

.modal-header {
    padding: 2px 16px;
    background-color: #5cb85c;
    color: white;
}

.modal-body {padding: 2px 16px;}

.modal-footer {
    padding: 2px 16px;
    background-color: #5cb85c;
    color: white;
}