You can center a box both vertically and horizontally, using the following technique :
display: table;
display: table-cell;
vertical-align: middle;
text-align: center;
display: inline-block;
If you use this technique, just add your table (along with any other content you want to go with it) to the content box.
body {_x000D_
margin : 0;_x000D_
}_x000D_
_x000D_
.outer-container {_x000D_
position : absolute;_x000D_
display: table;_x000D_
width: 100%;_x000D_
height: 100%;_x000D_
background: #ccc;_x000D_
}_x000D_
_x000D_
.inner-container {_x000D_
display: table-cell;_x000D_
vertical-align: middle;_x000D_
text-align: center;_x000D_
}_x000D_
_x000D_
.centered-content {_x000D_
display: inline-block;_x000D_
background: #fff;_x000D_
padding : 20px;_x000D_
border : 1px solid #000;_x000D_
}
_x000D_
<div class="outer-container">_x000D_
<div class="inner-container">_x000D_
<div class="centered-content">_x000D_
<em>Data :</em>_x000D_
<table>_x000D_
<tr>_x000D_
<th>Name</th>_x000D_
<th>Age</th>_x000D_
</tr>_x000D_
<tr>_x000D_
<td>Tom</td>_x000D_
<td>15</td>_x000D_
</tr>_x000D_
<tr>_x000D_
<td>Anne</td>_x000D_
<td>15</td>_x000D_
</tr>_x000D_
<tr>_x000D_
<td>Gina</td>_x000D_
<td>34</td>_x000D_
</tr>_x000D_
</table>_x000D_
</div>_x000D_
</div>_x000D_
</div>
_x000D_
See also this Fiddle!