I would like to make the box where you write messages just a little wider. What exactly do I have to change and where?

It's probably very easy, but I'm stuck. Help a girl out, please!

open up templates/main_post_form.html and look for this on line 25:

<td bgcolor={$tableParam[10]} class=cell1><textarea name=postText cols=38 rows=10 WRAP class=textForm>{$postText}</textarea>


change the 'cols=38' bit to a higher number, say 60.

or
<textarea name=postText cols=38 rows=10 WRAP class=textForm style="width:100%">

Thanks!