Cascading Style Sheets Level 2
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| Cascading Style Sheets Level 2 | |
|---|---|
| Name | Cascading Style Sheets Level 2 |
| Developer | World Wide Web Consortium |
| First release | 1998 |
| Latest release | 1998 (Recommendation) |
| Typing | Styling language |
| Website | https://www.w3.org/TR/CSS2/ |
Cascading Style Sheets Level 2 Cascading Style Sheets Level 2 is a specification produced by the World Wide Web Consortium that extended Cascading Style Sheets concepts with layout, visual formatting, and printing capabilities. It influenced implementations in major browsers such as Netscape Communications Corporation, Microsoft Internet Explorer, Opera Software, and later engines like WebKit, Blink (browser engine), and Gecko (software). The specification intersected with standards and organizations including IETF, W3C, W3C CSS Working Group, and impacted projects such as HTML 4.01, XHTML, and SMIL.
Overview
CSS2 introduced a structured model for presentation separate from markup used in HTML 4.01, XHTML 1.0, and other markup languages promoted by the World Wide Web Consortium. It defined cascading rules, specificity, inheritance, and the box model used by rendering engines like Trident (layout engine), KHTML, and Servo (browser engine). Authors of user agents such as Mozilla Foundation and companies like Apple Inc., Google LLC, and Microsoft Corporation referenced CSS2 for features related to paged media, absolute positioning, and generated content.
Modules and Features
The CSS2 Recommendation organized capabilities into thematic modules addressing layout, typography, and media. Notable features included the visual formatting model adopted in HTML 4.01 workflows, the box model underpinning engines like Blink (browser engine), positioning schemes used by Netscape Communications Corporation and Microsoft Corporation, and selectors shaping stylesheet rules in projects from Opera Software to Mozilla Foundation. CSS2 defined properties for fonts and text handling used alongside technologies from Adobe Systems and standards like ISO/IEC 10646. Print and paged media features aligned with work by W3C CSS Working Group and implementations in publishing tools from Quark, Inc. and Adobe Systems.
Syntax and Media Types
CSS2 formalized a grammar for rules that user agents parse, affecting parsers in WebKit and Gecko (software), and influenced tokenizer strategies described in documents from IETF. The syntax supported selectors, declarations, and at-rules used in authoring tools by entities such as Microsoft Corporation and Opera Software. Media types in CSS2 included screen, print, speech, and other categories coordinated with specifications from W3C, and related to initiatives like Accessible Rich Internet Applications (WAI-ARIA) promoted by W3C Web Accessibility Initiative and accessibility work from World Wide Web Consortium partners.
Implementation and Browser Support
Adoption of CSS2 features varied across vendors. Microsoft Internet Explorer implemented many CSS2 properties with vendor-specific behaviors that differed from Opera Software and Netscape Communications Corporation implementations. Later open-source projects such as Mozilla Foundation's Gecko (software) and WebKit-based browsers from Apple Inc. and Google LLC implemented CSS2 features progressively, while newer engines like Blink (browser engine) and experimental engines such as Servo (browser engine) refined parsing and layout. The interoperability challenges spurred compatibility tests by groups including W3C Test Suite contributors and initiatives at CERN and academic labs at Massachusetts Institute of Technology and Stanford University.
History and Standardization Process
The CSS2 specification emerged from earlier work on Cascading Style Sheets and extended concepts discussed at meetings involving the World Wide Web Consortium and contributors from Netscape Communications Corporation, Microsoft Corporation, Opera Software, Adobe Systems, and academic partners including University of Cambridge and University of Illinois Urbana–Champaign. The process included drafts, public mailing lists, and coordination with committees such as the W3C CSS Working Group and liaison with IETF and ISO. Major milestones included the publication of the CSS2 Candidate Recommendation and the W3C Recommendation in 1998, followed by errata and later modularization efforts that influenced successors like CSS Level 2.1 and Cascading Style Sheets Level 3 workstreams involving companies such as Google LLC, Apple Inc., Microsoft Corporation, and organizations like WHATWG.
Criticisms and Limitations
Practitioners and vendors critiqued CSS2 for ambiguities in the box model, inconsistencies across implementations from Microsoft Corporation and Netscape Communications Corporation, and limited layout primitives compared with proposals discussed in W3C groups. Web developers referenced issues in cross-browser rendering when comparing behavior in Mozilla Foundation and Opera Software browsers, prompting subsequent clarifications and the CSS2.1 effort with input from entities like Adobe Systems and testing efforts at W3C Test Suite. The modularization and extension process that followed involved stakeholders such as WHATWG and browser vendors including Google LLC and Apple Inc. to address shortcomings and expand capabilities in later specifications.