CSS round OK button

HTML

<a href="http://example.com" class="round-button">OK</a>

CSS

.round-button {
    display:block;
    width:50px;
    height:50px;
    line-height:50px;
    border: 2px solid #f5f5f5;
    color:#f5f5f5;
    text-align:center;
    text-decoration:none;
    background: #464646;
    box-shadow: 0 0 3px gray;
    font-size:20px;
    font-weight:bold;
}
.round-button:hover {
    background: #262626;
}