examples/intro/modal.html
<!DOCTYPE html>
<head>
	<title>Creating a modal window with HTML5 &amp; CSS3</title>
	
<!-- source: http://netdna.webdesignerdepot.com/uploads7/creating-a-modal-window-with-html5-and-css3/demo.html -->
	<style>
	.modalDialog {
		position: fixed;
		font-family: Arial, Helvetica, sans-serif;
		top: 0;
		right: 0;
		bottom: 0;
		left: 0;
		background: rgba(0,0,0,0.8);
		z-index: 99999;
		opacity:0;
		-webkit-transition: opacity 400ms ease-in;
		-moz-transition: opacity 400ms ease-in;
		transition: opacity 400ms ease-in;
		pointer-events: none;
	}

	.modalDialog:target {
		opacity:1;
		pointer-events: auto;
	}

	.modalDialog > div {
		width: 400px;
		position: relative;
		margin: 10% auto;
		padding: 5px 20px 13px 20px;
		border-radius: 10px;
		background: #fff;
		background: -moz-linear-gradient(#fff, #999);
		background: -webkit-linear-gradient(#fff, #999);
		background: -o-linear-gradient(#fff, #999);
	}

	.close {
		background: #606061;
		color: #FFFFFF;
		line-height: 25px;
		position: absolute;
		right: -12px;
		text-align: center;
		top: -10px;
		width: 24px;
		text-decoration: none;
		font-weight: bold;
		-webkit-border-radius: 12px;
		-moz-border-radius: 12px;
		border-radius: 12px;
		-moz-box-shadow: 1px 1px 3px #000;
		-webkit-box-shadow: 1px 1px 3px #000;
		box-shadow: 1px 1px 3px #000;
	}

	.close:hover { background: #00d9ff; }
	</style>
</head>

<body>

<a href="#openModal">Open Modal</a>

<div id="openModal" class="modalDialog">
	<div>
		<a href="#close" title="Close" class="close">X</a>
		<h2>Modal Box</h2>
		<p>This is a sample modal box that can be created using the powers of CSS3.</p>
		<p>You could do a lot of things here like have a pop-up ad that shows when your website loads, or create a login/register form for users.</p>
	</div>
</div>

</body>
</html>

source: http://netdna.webdesignerdepot.com/uploads7/creating-a-modal-window-with-html5-and-css3/demo.html