Just do this and you don’t need multiple margins or multiple classes:
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style>
.links{
width:270px;
}
.links a{
float:left;
margin:0 4px 8px 0;
width: 50px;
height: 50px;
background-color:green;
}
</style>
</head>
<body>
<div class="links">
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
<a href="" target="_blank"></a>
</div>
</body>
</html>