I have two tables on a page that I want to display side by side, and then center them within the page (actually within another div, but this is the simplest I could come up with):
<style>
#outer { text-align: center; }
#inner { text-align: left; margin: 0 auto; }
.t { float: left; }
table { border: 1px solid black; }
#clearit { clear: left; }
</style>
<div id="outer">
<p>Two tables, side by side, centered together within the page.</p>
<div id="inner">
<div class="t">
<table>
<tr><th>a</th><th>b</th></tr>
<tr><td>1</td><td>2</td></tr>
<tr><td>4</td><td>9</td></tr>
<tr><td>16</td><td>25</td></tr>
</table>
</div>
<div class="t">
<table>
<tr><th>a</th><th>b</th><th>c</th></tr>
<tr><td>1</td><td>2</td><td>2</td></tr>
<tr><td>3</td><td>5</td><td>15</td></tr>
<tr><td>8</td><td>13</td><td>104</td></tr>
</table>
</div>
</div>
<div id="clearit">all done.</div>
</div>
I understand that it's something to do with the fact that the tables are floated, but I'm at a loss as to understand what I'm missing. There are many web pages that describe something like the technique I show here, but in any event it doesn't work; the tables cling stubbornly to the left hand margin.
Unfortunately, all of these solutions rely on specifying a fixed width. Since the tables are generated dynamically (statistical results pulled from a database), the width can not be known in advance.
The desired result can be achieved by wrapping the two tables within another table:
<table align="center"><tr><td>
//code for table on the left
</td><td>
//code for table on the right
</td></tr></table>
and the result is a perfectly centered pair of tables that responds fluidly to arbitrary widths and page (re)sizes (and the align="center" table attribute could be hoisted out into an outer div with margin autos).
I conclude that there are some layouts that can only be achieved with tables.