Primero debes ver el vídeo CSS: selectores avanzados,
en el que se te muestran algunos selectores avanzados, como descendientes directos, elementos contiguos, :first-child, :first-letter, :first-line, valores de atributos, :lang, :after, :before.
The 30 CSS Selectors you Must Memorize: So you learned the base id, class, and descendant selectors – and then called it a day? If so, you’re missing out on an enormous level of flexibility. While many of the selectors mentioned in this article are part of the CSS3 spec, and are, consequently, only available in modern browsers, you owe it to yourself to commit these to memory.
Zen Coding: Zen Coding is an editor plugin for high-speed HTML, XML, XSL (or any other structured code format) coding and editing. The core of this plugin is a powerful abbreviation engine which allows you to expand expressions—similar to CSS selectors—into HTML code.
Zen Coding Cheat Sheets: You can download and print these cheat sheets for quick reference to Zen Coding syntax and abbreviations.
Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification: This specification defines Cascading Style Sheets, level 2 revision 1 (CSS 2.1). CSS 2.1 is a style sheet language that allows authors and users to attach style (e.g., fonts and spacing) to structured documents (e.g., HTML documents and XML applications). By separating the presentation style of documents from the content of documents, CSS 2.1 simplifies Web authoring and site maintenance.
CSS 2.1 builds on CSS2 which builds on CSS1. It supports media-specific style sheets so that authors may tailor the presentation of their documents to visual browsers, aural devices, printers, braille devices, handheld devices, etc. It also supports content positioning, table layout, features for internationalization and some properties related to user interface.
CSS 2.1 corrects a few errors in CSS2 (the most important being a new definition of the height/width of absolutely positioned elements, more influence for HTML's "style" attribute and a new calculation of the 'clip' property), and adds a few highly requested features which have already been widely implemented. But most of all CSS 2.1 represents a "snapshot" of CSS usage: it consists of all CSS features that are implemented interoperably at the date of publication of the Recommendation.
CSS 2.1 is derived from and is intended to replace CSS2. Some parts of CSS2 are unchanged in CSS 2.1, some parts have been altered, and some parts removed. The removed portions may be used in a future CSS3 specification. Future specs should refer to CSS 2.1 (unless they need features from CSS2 which have been dropped in CSS 2.1, and then they should only reference CSS2 for those features, or preferably reference such feature(s) in the respective CSS3 Module that includes those feature(s)).
Cascading Style Sheets, level 1: This document specifies level 1 of the Cascading Style Sheet mechanism (CSS1). CSS1 is a simple style sheet mechanism that allows authors and readers to attach style (e.g. fonts, colors and spacing) to HTML documents. The CSS1 language is human readable and writable, and expresses style in common desktop publishing terminology.
One of the fundamental features of CSS is that style sheets cascade; authors can attach a preferred style sheet, while the reader may have a personal style sheet to adjust for human or technological handicaps. The rules for resolving conflicts between different style sheets are defined in this specification.