Skinning

Skinning is the process of changing the look-n-feel of your Plone site.

Skinning Mouseover DOM Inspector
This is an indispensible tool for working with CSS. You can mouseover any element on a live webpage and see what it's CSS attributes are.
Skinning What you see - anatomy of a Plone page
This is a very useful tutorial which explains what templates and CSS control what you see and where are they located.