semi-transparent gradient

HTML

<a class="btn">button</a>

CSS

body {
    background: red;
}

a.btn { 
 color: #fff;
 display: block;
 text-align: center;
 font-weight: bold;
 text-decoration: none;
 padding: 10px 0px;

 background: -webkit-gradient(linear, left top, left bottom, from(rgba(0, 0, 0, 0.1)), to(rgba(0, 0, 0, 1)), color-stop(1,black));
}