History: CSS Overview
Preview of version: 8
Presentation
The presentation of elements, the visual style of your theme, is created using CSS (Cascading Style Sheets).
W3C provides tutorials and other tools for learning CSS principles: www.w3.org/Style/CSS. See also the CSS links in the Directory.
Tiki methodologies
You can start with an existing theme style sheet and copy, rename and modify it or, for Tiki 2, you can start with Tikiwiki2_CSS_selectors (which has a pretty complete set of the selectors and placeholder values in that Tiki version). Or you can start with an empty CSS file and create the new style from scratch.
New in Tiki 3: layout.css
As of Tiki 3.0, there is a layout.css file that provides basic layout selectors and properties and some default colors (and colors meant to be overridden by the theme stylesheet), which is imported by the theme stylesheet.
To start from an existing CSS file, see Modifying an Existing Style Sheet; to start from a blank CSS file, see Starting Fresh — CSS.