Hi Hal,
It depends on the basic TW you are using. A default/vanilla TW uses
PageTemplate, ViewTemplate, EditTemplate shadow tiddlers to define the
page layout.
The CSS definitions are also stored in shadow tiddlers:
Look at the right sidebar: Index: More: Shadowed
StyleSheetColors
StyleSheetLayout
StyleSheetLayout contains the default definitions. If you want to
change something use your StyleSheet tiddler. _Don't_ change the
shadow tiddlers.
To get the info, which ID or CLASS you have to change, you'll need a
development tool like: FireBug (plugin), if you use FireFox. If you
use Chrome you need to open Settings: Tools: Developer Tools (built
in). I don't use IE for this.
Most likely in your case it is near:
class = "tiddler" or
class = "viewer"
If you would have a link, to your TW, it would be easier.
===
I made a video some time ago, where you can see, how to work with
FireBug. You can change the CSS and see, what happens with the TW. If
you found the parameter you can change the tiddler. The video doesn't
exactly match your needs, but it shows, how you can find the right ID
or class name.
hope this helps.
mario
http://www.youtube.com/watch?v=JDieJXnc8ds&feature=player_detailpage#t=320s