Here is a small collection of articles about style sheets for on-line SGML & HTML, that I wrote to help discussions on the html-wg and www-html mailing lists. Also see the W3C's style sheet overview.
(Old) A proposal that used the syntax of X resource files, which eventually proved too limited. Most of this has been implemented. [31 Mar 1995]
A collection of slides that were used in the discussion at WWW'95 in Darmstadt. [18 Apr 1995]
An attempt to formulate the goals of the style sheet language. [30 May 1995]
A model to describe the process of formatting (not the same as an implementation, but a first implementation might be based on it.) [30 May 1995]
Requirements and constraints for associating style rules with SGML elements, including a stab at a syntax for this part of the style rules, based on the earlier proposal above, and Håkon Lie's cascading style sheets for Arena. [23 May 1995]
Rules for combining style sheets from different sources with different priorities. [11 May 1995]
Possible ways of making property values depend on the context, with suggestions for a syntax. [11 May 1995]
A number of difficult styles, that have no obvious and elegant expression as a property.
A proposed set of properties for selecting fonts, text styles, margins, line breaks, rules, and colors. [10 July 1995]
[under construction] Justification, indent, leading, numbering, etc.