Changing the Length of a Table

[Kodaks]

Hi,
I would like to shorten the "Author" column, and lengthen the "Message" column on my theme. Here is a screen shot:
   

I have been poking around the templates, but have not been able to find anything useful. How would I go about doing that? Thanks!

[gusto5]

in the template "showthread" change these values

<td class="tcat" [color=red]width="15%"[/color]><span class="smalltext"><strong>$lang->author</strong></span></td>
<td class="tcat" [color=red]width="85%"[/color]><span class="smalltext"><strong>$lang->message</strong></span></td>