Table of contents
- 1. Modules and the standardization process
- 2. CSS modules status
- 2.1. Stable modules
- 2.2. Modules in the refining phase
- 2.3. Modules in the revising phase
- 2.4. Modules in the exploring phase
CSS3 is the latest evolution of the Cascading Style Sheets language and aims at extending CSS2.1. It brings a lot of long awaited novelties, like rounded corners, shadows, gradients, transitions or animations, as well as new layouts like multi-columns, flexible box or grid layouts. Experimental parts are vendor-prefixed and should either be avoided in production environments, or used with extreme caution as both their syntax and semantic can change in the future.
Modules and the standardization process
CSS Level 2 needed 9 years, from August 2002 to June 2011 to reach the Recommendation status. This was due to the fact that a few secondary features hold back the whole specification. In order to accelerate the standardization of non-problematic features, the CSS Working Group of the W3C, in a decision referred as the Beijing doctrine, divided CSS in smaller components called modules. Each of these modules is now an independent part of the language and moves towards standardization at its own pace.  While some modules are already W3C Recommendations, other still are early Working Drafts. New modules are also added when new needs are identified.
Formally, there is no CSS3 standard per se. Each module being standardized independently, the standard CSS consists of CSS2.1 amended and extended by the completed modules, not necessary all with the same level number. At each point of time, a snapshot of the CSS standard can be defined, listing CSS2.1 and the mature modules.
Though today no module with a level greater than 3 is standardized, this will change in the future. Some modules, like Selectors 4 or CSS Borders and Backgrounds Level 4 already have an Editor's Draft, though they haven't reach the First Published Working Draft status.
CSS modules status
A few CSS modules are already fairly stable and have reached one of the three recommendation level of the CSSWG: Candidate Recommendation, Proposed Recommendation or Recommendation. These can be used without prefixed and are pretty stable, though a few features can still be dropped at the Candidate Recommendation stage.
These modules extend and amend the CSS2.1 specification which build the core of the specification. Together with it, they are the current snapshot of the CSS specification.
|CSS Color Level 3||Recommendation since June 7th, 2011|
It deprecates the system-color keywords that shouldn't be used in a production environment anymore.
|Selectors Level 3||Recommendation since September 29th, 2011|
The next iteration of the Selectors specification is already in progress, though it still hasn't reached the First Public Working Draft stage.
|CSS Namespaces Level 3||Recommendation since September 29th, 2011|
Adds the support for the XML Namespaces by defining the notion of CSS qualified name, using the '
|Media Queries Level 3||Proposed Recommendation|
Extends the former media type (
|CSS Style Attribute||Candidate Recommendation|
|Formally defines the syntax of the content of the HTML |
Backgrounds and Borders
|CSS Backgrounds and Borders Level 3||Candidate Recommendation|
The CSS4 iteration of the Backgrounds and Borders specification is already in progress, though it still hasn't reached the First Public Working Draft stage, it plans to add the ability to clip a border (with the CSS
properties) or to control the shape of the border in a corner (using the CSS
|CSS Multi-column Layout Module||Candidate Recommendation|
|Adds support for easy multi-column layouts using the CSS |
|CSS Speech Module||Candidate Recommendation|
|Defines the |
Though formally also at the Candidate Recommendation level, the CSS Marquee module didn't see any progress recently and should not be considered on the standard track right now.
Modules in the refining phase
Specifications that are deemed to be in the refining phase are already fairly stable. Though changes are still expected, they shouldn't create incompatibilities with current implementations; they should mainly define behavior in edge cases.
Basic User Interface
|CSS Basic User Interface Module Level 3||Working Draft|
An early list of what could be in the next iteration of the CSS Basic User Interface Module is available.
Image Values and Replaced Content
|CSS Image Values and Replaced Content Module Level 3||Candidate Recommendation|
Values and Units
|CSS Values and Units Module Level 3||Working Draft|
Formally defines the CSS data types of CSS 2.1, that were implicitely defined by their grammar token and some textual precisions.
Modules in the revising phase
Modules that are in the revising phase are much less stable than those in the refining phase. Often the syntax is still under scrutiny and may evolve a lot, in a non-compatible way. Alternative syntax are tested and often implemented.
|CSS Text Level 3||Working Draft|
A few features present in early CSS Text Level 3 draft have being postponed to the next iteration of this module.
|CSS Transitions||Working Draft|
|Allows the definition of transitions effects between two properties values by adding the CSS |
|CSS Animations||Working Draft|
|Allows the definition of animations effects by adding the CSS |
|CSS Transforms||Working Draft|
|CSS Fonts Module Level 3||Working Draft|
Amends the CSS2.1 Font matching algorithm to be closer to what is really implemented.
Flexible box layout
|CSS Flexible Box Layout Module||Working Draft|
|Add a flexbox layout to the CSS |
Modules in the exploring phase
|CSS Conditional Rules Module Level 3||Working Draft|
|Adds features for conditional processing of parts of style sheets, conditioned on capabilities of the browser or the document the style sheet is being applied to. It consists mainly in allowing nested at-rules inside |
|CSS Device Adaptation||Working Draft|
|Adds a new at-rule, |
|CSS Grid Layout||Working Draft|
Adds a new layout based on a grid.
Note: there are current experiment towards merging this specification with the CSS Template Layout.
|CSS Template Layout Module||Working Draft|
Adds a new layout based on grid templates.
|CSS Generated Content for Paged Media Module||Working Draft|
|Adds the ability to tailor printed version of a document by allowing to control header, footer but also references tables like indexes or tables of content.|
Exclusions and Shapes
|CSS Exclusions and Shapes Module Level 3||Working Draft|
|Extends the floats mechanism to define exclusion regions in any positioning scheme. Adds the notion of shapes, in which content must flows.|
|CSS Lists and Counters Module Level 3||Working Draft|
|Extends the list counter mechanism so that list markers can be styled and Web developers can define new list counter schemes.|
|CSS Regions Module Level 3||Working Draft|
|Defines a new mechanism allowing content to flow across, eventually non-contiguous, multiple areas called regions.|
|CSS Variables Module Level 1||Working Draft|
|Defines a mechanism allowing to define variables in CSS.|
|CSS Fragmentation Module Level 3||Working Draft|
|Defines how partitions of a Web page should happen, that is page, column breaks, and widows and orphans handling.|