The following will make your forum fit into a table:
Put this at the very top of the header section. Also, your forum MUST BE enabled for HTML. To do that, if it is not, you MUST follow THIS LINK and ask for it to be HTML enabled.
<div align="center">
<!-- NOTE, change the following width to match the size of your overall table -->
<table width="800">
<tr>
<td>
<!-- PUT ALL OF YOUR FORUM HEADER CODE HERE. -->
Put this at the end the footer section:
<!-- PUT ALL OF YOUR FORUM FOOTER CODE HERE. -->
</td>
</tr>
</table>
</div>
The above will make your entire forum 800 pixels wide. Note, if anyone posts a picture wider than 800 pixels, it will stretch the forum past 800 pixels wide.
Here's a tip for copying and pasting code like this.
Copy the code into a simple text editor like Windows Notepad.
Do not use a word processor or other rich text editor.
Then copy that text into your HTML editor.
If you copy this code directly into an HTML editor like FrontPage or DreamWeaver, it will alter the code.