<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.box{ animation: change 1s ease-in infinite ; display:block; width:0;
height:0;
border-left:10px solid transparent;
border-right:10px solid transparent;
border-bottom:10px solid #f00;}
@keyframes change {
0%{ opacity:0;}
50%{ opacity:1;}
100%{ opacity:0;}
}
</style>
</head>
<body>
<a class="box"> </a>
</body>
</html>