Live Demo: Example of CSS3 opacity Property Animation

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Example of CSS3 opacity Property Animation</title>
<style>
.container{
	width: 300px;
	height: 200px;
	position: relative;
	background: #db75d6;
	border: 5px solid #a0299a;
}
.animated {
    opacity: 0;
	width: 200px;
	padding: 75px 0;
	margin: 50px;
	font: bold 46px sans-serif;
	background: #6f5ece;
	outline: 5px solid #4936b4;
	text-align: center;	
    -webkit-animation: test 4s infinite; /* Chrome, Safari, Opera */
    animation: test 4s infinite;
}
/* Chrome, Safari, Opera */
@-webkit-keyframes test {
    50% {opacity: 1;}
}
/* Standard syntax */
@keyframes test {
    50% {opacity: 1;}
}
</style>
</head>
<body>
	<p><strong>Warning:</strong> CSS Animations do not work in Internet Explorer 9 and earlier versions.</p>
	<p><strong>Note:</strong> The opacity (i.e. transparency) of the blue DIV box is animating from its initial value "0" to "1", and back to the initial value "0" again up to infinite times.<p>
	<div class="container">
		<div class="animated">Box</div>
	</div>
</body>
</html>