Center content of the guestbook

[proticamp]

Hi again and congratulation for your good work!
I wonder about how to center the content of my guestbook. My guestbook is this one. I don't know html, but searching and... improvisating, I entered the followinig code to guestbook header:

<div style="text-align: center;">
  <img border="0" align="middle" src="http://www.mysite.com/image.jpg" alt="" /></div><span class="head-text" style="font-family: Tahoma; font-size: 10pt;"><span style="font-size: 10pt;"></span><span style="font-size: 10pt;"></span></span><br />
<span class="head-text" style="font-family: Tahoma; font-size: 10pt;"><span style="font-size: 10pt;"></span></span>
<div style="text-align: center;"><br />
  </div>
<table>
</table>
<table width="80%">
  <tbody>
    <tr>
      <td style="width: 25%;"><br />
        </td>
      <td style="font-family: Verdana;">
        <p align="justify"><span style="font-size: 10pt;">Welcome message</td>
    </tr>
  </tbody>
</table>

When viewing in Firefox 1.5, it's OK (although the center position of the welcome message is different when changing screen resolution, but that's not a problem, because every time the text is centered).

But in IE 6 the text of the guestbook does not apper centered, as in Firefox, but moved on the right

Could you test it and propose me a solution to put all my guestbook content at the center of the page? (the image is easy, by selecting center alignment but the text? I don't want to transform it to an image and center it, it must be something else, like a table maybe...)
Thanks.

By the way, I like you forum GUI!!! Is it a ready-to-use PHP template that makes it so lovely?