Adjusting the table width

Is there an alternative way to adjusting the width of the entire guestbook instead of going into the Styles Setting section? If so, can you please direct me to the file(s). For some reason when I try to update information in the styles section, it causes my website to have a "500" error and my site crashes and I have to contact my host to put it up back up.

Thanks.

Edit body.php in templates.

Thanks so much. That worked!