User CSS Overrides
User CSS in Spaz allows the user to change any aspect of the current theme's appearance.
User CSS code is stored in the user.css file in the
app's preferences directory. You can edit this file with any text
editor, or you can use the built-in editor in Spaz. To open the
built-in editor, click the "Edit User CSS" button in Preferences
> Interface.

Here are some simple examples of how to override the current theme with your own "hacks." Note that these may not work for all themes.
If you have your own CSS hacks to share, let us know! Post them in the discussions on http://help.getspaz.com