Web Style Sheets home page
What are style sheets?
Style sheets describe how documents are presented on screens, in
print, or perhaps how they are pronounced. W3C has actively
promoted the use of style sheets on the Web since the Consortium
was founded in 1994. The Style Activity has
produced several W3C Recommendations (CSS1, CSS2, XPath, XSLT). CSS especially is widely implemented in browsers.
By attaching style sheets to structured documents on the Web
(e.g. HTML), authors and readers can influence the presentation of
documents without sacrificing device-independence or adding .
The easiest way to start experimenting with style sheets is to
find a browser that supports
CSS. Discussions about style sheets are carried out on the www-style@w3.org mailing
list and on comp.infosystems.www.authoring.stylesheets.
The W3C Style Activity is also developing XSL, which consists of a combination of XSLT and “Formatting Objects”
(XSL-FO).
Why two Style Sheet languages?
The fact that W3C has developed XSL in addition to CSS has
caused some confusion. Why develop a second style sheet language
when implementors haven't even finished the first one? The answer
can be found in the table below:
|
| CSS
| XSL
|
| Can be used with HTML?
| yes
| no
|
| Can be used with XML?
| yes
| yes
|
| Transformation language?
| no
| yes
|
| Syntax
| CSS
| XML
|
The unique features are that CSS can be used to style HTML &
XML documents. XSL, on the other hand, is able to transform
documents. For example, XSL can be used to transform XML data into
HTML/CSS documents on the Web server. This way, the two languages
complement each other and can be used together.
Both languages can be used to style XML
documents.
CSS and XSL use the same underlying formatting model and
designers therefore have access to the same formatting features in
both languages. W3C will work hard to ensure that interoperable
implementations of the formatting model are available.
A W3C Note on "Using XSL and
CSS together" is available.
Press clippings
If you are new to the subject, you may want to start by reading
some press clippings on style sheets:
See the CSS and XSL
pages for more (and more recent) articles.
CSS
Cascading Style Sheets (CSS) is a style
sheet mechanism that has been specifically developed to meet the
needs of Web designers and users.
XSL
W3C's XSL Working Group developed the eXtensible Style Language.
(As of 2016, the Working Group is not active.) XSL builds on DSSSL
and CSS and is primarily targeted for highly structured XML data
which, e.g., needs element reordering before presentation. For more
information on XSL see the W3C XSL resource page.
DSSSL
DSSSL is a document tree transformation and style language in
with many adherents in the SGML community. DSSSL resources on the
Web:
CSS-DOM & SAC
A CSS file can be created and edited “by hand,” i.e., with a
text editor, but you can also write a program in ECMAscript, Java
or some other language, that manipulates a style sheet. This is in
fact so common, that there are software libraries of useful
functions available. To help in porting such program &
libraries to different computer platforms, W3C has developed a
specification called CSS-DOM, that defines a set of
functions that all such libraries must provide.
The CSS Document Object Model is an API (Abstract
Programming Interface) for manipulating CSS (and to a certain
extent also other style languages) from within a program. An API is
the specification of a software library. You can see it as a
manual: it describes the functions and their parameters, but
doesn't contain the actual code.
There are several CSS-DOM libraries available, for different
platforms. Many of them are free. Many browsers have a CSS-DOM
library built-in, for use by ECMAScript programs.
SAC (Simple API for CSS) is a complement to the CSS-DOM. The
CSS-DOM contains functions to manipulate a style sheet after it has
been loaded into memory; the functions defined by SAC help in parsing a style sheet, i.e., in transferring a style sheet
from a file into memory.
The CSS-DOM is a W3C
Recommendation. SAC is a project under
development. Some software (other than
browsers) is listed on the CSS overview page.
Conferences, workshops, research
The W3C team and representatives of W3C members often give presentations.
Dynamic HTML
Dynamic HTML is a term used to describe HTML pages with dynamic
content. CSS is one of three components in
dynamic HTML; the other two are HTML
itself and JavaScript (which is being standardized under the name
EcmaScript). The three components are glued together with DOM, the Document Object Model.
On 17 December 2016, CSS was 20
years old!