Abstract
This specification defines in general a subset of CSS 2.1 [CSS21] that is to be considered a
baseline for interoperability between implementations of CSS on constrained devices (e.g.
mobile phones). Its intent is not to produce a profile of
CSS incompatible with
the complete specification, but rather to ensure that implementations that
due to platform limitations cannot support the entire specification
implement a common subset that is interoperable not only amongst
constrained implementations but also with complete ones. Additionally,
this specification aligns itself as much as possible with the OMA's Wireless CSS 1.1 [WCSS11] specification.
Status of this document
This section describes the status of this document at the time of
its publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the W3C technical reports
index at http://www.w3.org/TR/.
Publication as a Working Draft does not imply endorsement by the W3C
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obsoleted by other documents at any time. It is inappropriate to cite this
document as other than work in progress.
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This document was produced by the CSS
Working Group (part of the Style Activity).
This document was produced by a group operating under the 5 February
2004 W3C Patent Policy. W3C maintains a public list of any patent
disclosures made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent. An
individual who has actual knowledge of a patent which the individual
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Claim(s) must disclose the information in accordance with section 6 of the
W3C Patent Policy.
Table of Contents
1. Introduction
This document specifies a profile of CSS that is a subset of CSS 2.1 [CSS21].
The key words of descriptive assertions and RFC 2119 terminology. The
key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to
be interpreted as described in RFC 2119 [RFC2119].
Since the goal of this specification is to define a baseline
interoperability level, user agents MAY accept CSS documents conforming to CSS 2.1 or subsequent revisions of the CSS family of Recommendations.
In order to conform to this specification, user agents, authoring
tools, and content MUST conform to the Conformance and Error conditions section of the
CSS 2.1 specification [CSS21], with the
following modifications.
- Only features marked as supported in this specification are REQUIRED, support
for a larger set of CSS
2.1 is OPTIONAL.
- The requirement concerning which CSS 2.1 media types are supported is tightened so
that both the
handheld and all media types MUST be accepted
and processed. Other media types MAY be accepted and processed as well.
- The requirements that user agents MUST make it possible to select an alternate style
sheet amongst those linked from the document, as well as provide for a
way to turn off author style sheets, are relaxed to be RECOMMENDED behavior, but not
REQUIRED.
3. Selectors
Selectors are defined in the Selectors chapter of the CSS 2.1 specification [CSS21]. The following
table identifies which selector constructs MUST be supported amongst those
defined by CSS 2.1.
| Selector type
| Example
| Meaning
|
| Universal
selector
| *
| Matches any element.
|
| Type selectors
| E
| Matches any E element.
|
| Descendant
selectors
| E F
| Matches any F element that is a descendant of an E element.
|
| Child
selectors
| E > F
| Matches any F element that is a child of an element E.
|
| The link
pseudo-classes
| E:link
| Matches element E if E is the source anchor of a hyperlink,
unvisited by a user.
|
| The link
pseudo-classes
| E:visited
| Matches element E if E is the source anchor of a hyperlink, visited
by a user.
|
| The dynamic
pseudo-classes
| E:active
| Matches element E if E is being activated by the user.
|
| The dynamic
pseudo-classes
| E:focus
| Matches element E if E has the focus (accepts keyboard events or
other forms of text input).
|
| Class selectors
| .warning
| Language specific. (In (X)HTML, matches elements whose
class attribute contains a token with the same name.)
|
| ID selectors
| #myid
| Matches any element with an ID equal to "myid".
|
| Grouping
| E1, E2, E3 { ... }
| Matches a group of elements, which share the same style
declarations.
|
Should Namespace selectors (a CSS level 3 feature, see
[SELECT]) also be
required?
4. At-rules
At-rules are defined in the At-rules section of the
CSS 2.1 specification [CSS21]. The following
table identifies which at-rule constructs MUST be supported amongst those defined by
CSS 2.1.
| Rule
| Definition
|
| @charset
| Defines character set for the style sheet.
|
| @import
| Imports an external style sheet.
|
| @media
| Groups a set of style rules to apply only to one or more particular
media.
|
5. Properties
Properties are defined in the in several chapters of the CSS 2.1 specification [CSS21]. The following
table identifies which properties MUST be supported amongst those defined by CSS 2.1, as well as their syntax
(expressed using the same value
specifications as CSS 2.1) when it is subsetted from the original.
Limitations that apply to a property apply equally to its shorthand
alternative.
- Content Providers will reach a larger and more
satisfied audience by following Mobile Web Best Practices [MOBILE-BP] and
CSS Techniques for Web
Content Accessibility Guidelines [WCAG10-CSS-TECHS].
- The OMA's Wireless CSS 1.1 [WCSS11] introduced three extensions
'Marquee', 'Access Keys' and
'Input'. These extensions are not part of this
specification.
6. Syntax
A user agent MUST support all value types defined in the Values section of the CSS 2.1 specification [CSS21], with the
following exceptions:
- Support for counter
values is OPTIONAL
- Support for CSS2 System
Colors and User preferences
for fonts is OPTIONAL.
Acknowledgments
The editors wish to thank the authors of the previous version of this
document, Ted Wugofski (Openwave), Doug Dominiak (Openwave,formerly
Motorola), Peter Stark (Ericsson), and Tapas Roy (Openwave), as well as
the authors of the OMA
Wireless CSS
specification and the CSS 2.1 specification. Furthermore, the editors want to
thank the CDF
WG for their participation on
this specification.
References
Normative references
-
- [CSS21]
- Bert Bos; et al. Cascading Style Sheets, level 2 revision
1. 11 April 2006. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2006/WD-CSS21-20060411
- [RFC2119]
- S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. Internet RFC 2119. URL: http://www.ietf.org/rfc/rfc2119.txt
-
- [MOBILE-BP]
- Jo Rabin; Charles McCathieNevile. Mobile Web Best Practices 1.0,
Basic Guidelines. 2 November 2006. W3C Proposed Recommendation.
URL: http://www.w3.org/TR/2006/PR-mobile-bp-20061102
- [SELECT]
- Daniel Glazman; Tantek Çelik; Ian Hickson (eds).
Selectors. 15 December 2005. W3C Working Draft. (Work in
progress.) URL: http://www.w3.org/TR/2005/WD-css3-selectors-20051215
- [WCAG10-CSS-TECHS]
- Wendy Chisholm; Gregg Vanderheiden; Ian Jacobs. CSS Techniques
for Web Content Accessibility Guidelines 1.0. 6 November 2000. W3C
Note. URL: http://www.w3.org/TR/2000/NOTE-WCAG10-CSS-TECHS-20001106
- [WCSS11]
- Open Mobile Alliance. Wireless CSS Specification. 9 June
2004. Candidate Version 1.1. URL: http://www.openmobilealliance.org/release_program/docs/Browsing/V2_2-20040609-C/OMA-WAP-WCSS-V1_1-20040609-C.pdf