[Freesteyelz]

Consider duplicating your current Style and save it. In Styles & Templates --> Download/Upload Styles upload that style you've just saved. For "Allow User Selection" check "No". Experiment with it as you desire. To view your changes go to vB Options --> Style & Language Settings and set the style to "Default". If for any reason you don't like the changes just switch back your style to the previous one you had in "Style & Language Settings". That way you can run wild on a live board with minimal consequences.

Just for your information, you can also set up a testing board for this purpose. It's not to be made public but it's a way for you to test hacks and style changes without affecting your live board. Just a thought.