Good answer ppollono. I was just playing around and I got a slightly better solution. The CSS would remain the same, i.e. :
html, body, .container {
height: 100%;
}
.container {
display: table;
vertical-align: middle;
}
.vertical-center-row {
display: table-cell;
vertical-align: middle;
}
But for HTML:
<div class="container">
<div class="vertical-center-row">
<div align="center">TEXT</div>
</div>
</div>
This would be enough.