Centering Text

Hi!

In a PHP page, I have the following code:

<tr>
<td colspan=2 style="vertical-align: top">
<p style="margin: 10px; font-weight:bold; font-size:125%;">
<span style="text-align: center;">Lea things you should know about art!</span>
<br><br>
The Galleseum ...
<br><br>
</p>
</td>
</tr>

But the text "Lea..." is not centered.

In the same page, I have the following code that does work:

</td>
<td style="width: 15%; vertical-align: top; text-align:center;">Past Topics</td>
</tr>

What am I doing wrong?

Thank you!

Dr. T