Centering using CSS tables

HTML

<div class="content">
<ul class="center">
    <li class="v-align">
        <a href="/joomla31/">Somos</a>
    </li>
</ul>
</div>

CSS

.content {
    display: table;
}
.center {
    display: table-row;
    width: 90px;
    height: 90px; 
    border: 1px dotted blue;
}
.v-align {
    padding: 10px;
    border: 1px dashed green;
    display: table-cell;
    text-align: center;
    vertical-align: middle;
    height:60px;
    width:60px;
}