Netscape 4 version browser supports (at least partially) css1 (the W3C cascading style sheet specification recommended in December 1996) and thus gives TNRCC developers more means to define and control Web page presentation.
If style sheets are a new Web concept, Brian Wilson's Cascading Style Sheets FAQ at the Index Dot Html site asks and answers some good questions. Here's the answer to question 1, "What are Cascading Style Sheets?":
A Cascading Style Sheet (CSS) is a list of statements (also known as rules) that can assign various rendering properties to HTML elements. Style rules can be specified for a single element occurrence, multiple elements, an entire document, or even multiple documents at once. It is possible to specify many different rules for an element in different locations using different methods. All these rules are collected and merged (known as a "cascading" of styles) when the document is rendered to form a single style rule for each element.
This document is meant to provide an introduction to cascading style sheets and their use. Since background and text color are among the properties that style sheets can set, it also presents a collection of information on the browser safe color palette and the hexadecimal values to identify colors.
The classic book on the subject (copyright 1997) is Cascading Style Sheets: Designing for the Webby Hakon Wium Lie and Bert Bos. There's an excellent discussion of design principles in Chapter 13: Style Sheets with Style.
The World Wide Web Consortium is the standards-setting body for Web matters and thus the chief authority on style sheets. The W3C site has helpful documentation and tools at W3C Cascading Style Sheets Resources. W3C even provides eight W3C Core Styles that can be LINKed and used.
The Web Design Group's Site offers Cascading Style Sheets and CSS Check rule and syntax checker.
Builder.com formerly provided a CSS Reference Table http://www.builder.com/Authoring/CSS/table.html.
Also of note are presentations on Cascading Style Sheets at Webreference.com and Web Developer's Virtual Library.
And HotWired's webmonkey/stylesheets offers good materials, too, including an excellent 5-part tutorial by Steve Muldur.
Finally, here's Lie & Bos' appendix on HTML for style sheets, which Kay Keys scanned in and doctored up to help you integrate CSS and HTML concepts and constructs.
For getting into color, here's a start: Light, Color, and Healing.