Try something like this perhaps:
<a href="/retrieve/" class="button retrieve">Retrieve</a>
<style type="text/css" media="screen">
.button {
font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
text-decoration:none;
color:#fff;
background-color:green;
margin:1em;
padding:0.5em 1em;
font-size:2em;
text-transform:uppercase;
letter-spacing:0.1em;
}
</style>
http://jsfiddle.net/zdYbM/