If you're restyling the wiki, it's very useful to open the developer tools and use the inspector (in chrome for mac, I can press opt-command-j to open the console and the inspector is the left-most tool, it looks like a cursor, clicking a small rectangle. I think all the browsers have equivalent tools).
Hovering over page elements should then highlight them and display the element type, along with any classes and ids that they have.
If you click on an element, you should see a styles pane in the console that will let you fiddle with the css and see your changes reflected immediately (though they won't be persisted).
Regards,
Richard