The CSS saga
The saga of CSS starts in 1994. Håkon Wium Lie works at
CERN – the cradle of the Web – and the Web is starting
to be used as a platform for electronic publishing. One crucial
part of a publishing platform is missing, however: There is no way
to style documents. For example, there is no way to describe a
newspaper-like layout in a Web page. Having worked on personalized
newspaper presentations at the MIT Media Laboratory, Håkon
saw the need for a style sheet language for the Web.
Style sheets in browsers were not an entirely new idea. The
separation of document structure from the document's layout had
been a goal of HTML from its inception in 1990. Tim Berners-Lee
wrote his NeXT browser/editor in such a way that he could
determine the style with a simple style sheet. However, he didn't
publish the syntax for the style sheets, considering it a matter
for each browser to decide how to best display pages to its users.
In 1992, Pei Wei developed a browser called
had its own style sheet language.
However, the browsers that followed offered their users fewer
and fewer options to influence the style. In 1993, NCSA Mosaic,
the browser that made the Web popular, came out. Stylewise,
however, it was a backward step because it only allowed its users
to change certain colors and fonts.
Meanwhile, writers of Web pages complained that they didn't have
enough influence over how their pages looked. One of the first
questions from an author new to the Web was how to change fonts
and colors of elements. At that time, HTML did not provide this
functionality – and rightfully so. This excerpt from a
message sent to the www-talk mailing list early in 1994
gives a sense of the tensions between authors and implementors:
In fact, it has been a constant source of delight for me over
the past year to get to continually tell hordes (literally) of
people who want to -- strap yourselves in, here it comes --
control what their documents look like in ways that would be
trivial in TeX, Microsoft Word, and every other common text
processing environment: "Sorry, you're screwed."
The author of the message was Marc Andreessen, one of the
programmers behind NCSA Mosaic. He later became a co-founder of
Netscape, a company eager to fulfill the request of authors. On
October 13, 1994, Marc Andreessen announced to www-talk
that the first beta release of Mozilla (which later turned into
Netscape Navigator) was available for testing. Among the new tags
the new browser supported was center,
and more tags were to follow shortly.
Three days before Netscape announced the availability of its new
browser, Håkon published the first draft of the
Cascading HTML Style Sheets proposal. Behind the scenes,
Dave Raggett (the main architect of HTML 3.0) had encouraged the
release of the draft to go out before the upcoming
the Web conference in Chicago. Dave had realized that HTML
would and should never turn into a page-description language and
that a more purpose-built mechanism was needed to satisfy
requirements from authors. Although the first version of the
document was immature, it provided a useful basis for discussion.
Among the people who responded to the first draft of CSS was
Bert Bos. At that time, he was
building Argo, a highly customizable browser with style sheets,
and he decided to join forces with Håkon. Both of the two
proposals look different from present-day CSS, but it is not hard
to recognize the original concepts.
One of the features of the Argo style language was that it was
general enough to apply to other markup languages in addition to
HTML. This also became a design goal in CSS and
soon removed from the title of the specification. Argo also had
other advanced features that didn't make it into CSS1, in
particular, attribute selectors and generated text. Both features
had to wait for CSS2.
Cascading Style Sheets wasn't the only proposed style
language at the time. There was Pei Wei's language from the Viola
browser, and around 10 other proposals for style sheet languages
were sent to the www-talk and www-html mailing
lists. Then, there was DSSSL, a complex style and transformation
language under development at ISO for printing SGML documents.
DSSSL could conceivably be applied to HTML as well. But, CSS had
one feature that distinguished it from all the others: It took
into account that on the Web, the style of a document couldn't be
designed by either the author or the reader on their own, but that
their wishes had to be combined, or
cascaded, in some way;
and, in fact, not just the reader's and the author's wishes, but
also the capabilities of the display device and the browser.
As planned, the initial CSS proposal was presented at the Web
conference in Chicago in November 1994. The presentation at
Developer's Day caused much discussion. First, the concept of a
balance between author and user preferences was novel. A
fictitious screen shot showed a slider with the label
on one side and
author on the other. By adjusting the
slider, the user could change the mix of his own preferences and
those of the author. Second, CSS was perceived by some as being
too simple for the task it was designed for. They argued that to
style documents, the power of a full programming language was
needed. CSS went in the exact opposite direction by making a point
out of being a simple, declarative format.
At the next WWW conference in April 1995, CSS was presented
again. Both Bert and Håkon were there (in fact, this was the
first time they met in person) and this time, they could also show
implementations. Bert presented the support for style sheets in
Argo, and Håkon showed a version of the Arena browser that
had been modified to support CSS. Arena had been written by Dave
Raggett as a testbed for new ideas, and one of them was style
sheets. What started out as technical presentations ended up in
political discussions about the author-reader balance.
Representatives from the
author side argued that the author
ultimately had to be in charge of deciding how documents were
presented. For example, it was argued that there may be legal
requirements on how warning labels had to be printed and the user
should not be able to reduce the font size for such warnings. The
other side, where Bert and Håkon belong, argued that the
user, whose eyes and ears ultimately have to decode the
presentation, should be given the last word when conflicts
Outside of the political battles, the technical work continued.
The www-style mailing list was created in May 1995, and
the discussions there have often influenced the development of the
CSS specifications. Almost 10 years later, there were more than
16,000 messages in the archives of the mailing list. And after 20
years, more than 80,000!
In 1995, the World Wide Web Consortium (W3C) also became
operational. Companies were joining the Consortium at a high rate
and the organization became established. Workshops on various
topics were found to be a successful way for W3C members and staff
to meet and discuss future technical development. It was therefore
decided that another workshop should be organized, this time with
style sheets as the topic. The W3C technical staff working on
style sheets (namely Håkon and Bert) were now located in
Sophia-Antipolis in Southern France where W3C had set up its
European site. Southern France is not the worst place to lure
workshop participants to, but because many of the potential
participants were in the U.S., it was decided to hold the workshop
in Paris, which is better served by international flights. The
workshop was also an experiment to see if it was possible for W3C
to organize events outside the U.S. Indeed, this turned out to be
possible, and the workshop was a milestone in ensuring style
sheets their rightful place on the Web. Among the participants was
Thomas Reardon of Microsoft, who pledged support for CSS in
upcoming versions of Internet Explorer.
At the end of 1995, W3C set up the HTML Editorial Review Board
(HTML ERB) to ratify future HTML specifications. Because style
sheets were within the sphere of interest of the members of the
new group, the CSS specification was taken up as a work item with
the goal of making it into a W3C Recommendation. Among the members
of the HTML ERB was Lou Montulli of Netscape. After Microsoft
signaled that it was adding CSS support in its browser, it was
also important to get Netscape on board. Otherwise, we could see
the Web diverge in different directions with browsers supporting
different specifications. The battles within the HTML ERB were
long and hard, but CSS level 1 finally emerged as a W3C
Recommendation in December 1996.
In February 1997, CSS got its own working group inside W3C and
the new group set out to work on the features which CSS1 didn't
address. The group was chaired by Chris Lilley, a Scotsman
recruited to W3C from the University of Manchester. CSS
level 2 became a Recommendation in May 1998. Since then, the
group has worked in parallel on new CSS modules and errata for
The W3C working group has members (around 15 in 1999, around 115
in 2016) who are delegated by the companies and organizations
that are members of W3C. They come from all over the world, so the
meetings are usually over the phone, and last about an hour
every week. About four times each year, they meet somewhere in the
The CSS saga is not complete without a section on browsers. Had
it not been for the browsers, CSS would have remained a lofty
proposal of only academic interest. The first commercial browser
to support CSS was Microsoft's Internet Explorer 3, which was
released in August 1996. At that point, the CSS1 specification had
not yet become a W3C Recommendation and discussions within the
HTML ERB were to result in changes that Microsoft developers, led
by Chris Wilson, could not foresee. IE3 reliably supports most of
the color, background, font, and text properties, but it does not
implement much of the box model.
The next browser to announce support for CSS was Netscape
Navigator, version 4.0. Since its inception, Netscape had
been skeptical toward style sheets, and the company's first
implementation turned out to be a half-hearted attempt to stop
Microsoft from claiming to be more standards-compliant than
Netscape. The Netscape implementation supports a broad range of
features – for example, floating elements – but the
Netscape developers did not have time to fully test all the
features that are supposedly supported. The result is that many
CSS properties cannot be used in Navigator 4.
Netscape implemented CSS internally by translating CSS rules
scripts. The company also decided to let developers write JSSS,
thereby bypassing CSS entirely. If JSSS had been successful, the
Web would have had one more style sheet than necessary. This,
fortunately for CSS, turned out not to be the case.
Meanwhile, Microsoft continued its efforts to replace Netscape
from the throne of reigning browsers. In Internet Explorer 4,
the browser display engine, which among other things is
responsible for rendering CSS, was replaced by a module code-named
Trident. Trident removed many of the limitations in IE3,
but also came with its own set of limitations and bugs. Microsoft
was put under pressure by the Web Standards Project (WaSP), which
IE's Top 10 CSS Problems in November 1998 (see
Subsequent versions of Internet Explorer have considerably
improved the support for CSS.
The third browser that ventured into CSS was Opera. The browser
from the small Norwegian company made headlines in 1998 by being
tiny (it fit on a floppy!) and customizable while supporting most
features found in the larger offerings from Microsoft and
Netscape. Opera 3.5 was released in November 1998, and
supported most of CSS1. The Opera developers (namely Geir
Ivarsøy) also found time to test the CSS implementation
before shipping, which is a novelty in this business. Håkon,
was so impressed with Opera's technology that he joined the
company as CTO in 1999. One important market for Opera's browser
is mobile phones. By reformatting pages to fit on a small screen
@media is handy here), the Web has been
freed from the desktop (see Figure 2).
The people at Netscape responded to the increasing competition
with a move that was novel at the time: They released the source
code for the browser. With the source code public, anyone could
inspect the internals of their product, improve it, and make
competing browsers based on in. Much of the code, including the
CSS implementation, was terminated shortly after the release, and
Mozilla project was formed to build a new generation
browser. CSS was in important specification to handle and
countless hours have been spent by volunteers to make sure pages
are displayed according to the specification. Several browsers
have been based on the Mozilla code, including Galeon and Firefox.
Apple is often seen as a technology pioneer, but for a long
time, it did not spend much resources on Web browsers. Apple left
it to Microsoft to build a browser for its machines, and Internet
Explorer for Mac actually had better support for CSS than the
Windows version of the browser. In 2003, Microsoft discontinued
support for the Mac and Apple announced a new browser called
Safari. Safari isn't entirely new – it is based on
the open source Konqueror browser, which was developed for the KDE
system running on Linux.
For Web designers, it is good news to have several competing
products based on Web standards. Although some efforts to test
that your pages display well in all browsers are necessary, the
fact that Web pages can be displayed on a wide range of machines
is a huge improvement from the past:
Anyone who slaps a
this page is best viewed with Browser
X label on a Web page appears to be yearning for the bad old
days, before the Web, when you had very little chance of reading
a document written on another computer, another word processor,
or another network.
– Tim Berners-Lee in
Technology Review, July 1996
The CSS saga isn't only about Web browsers. Many people outside
of the few that program Web browsers have made important
contributions to CSS over the past years.
The CSS1 test suite was a landmark development for CSS
When the first two CSS implementations came out and could be
compared, we realized there was a problem. You could not expect
the style sheet tested only in one browser to work in the other
browser. To rectify the situation, Eric Meyer – with help
from countless other volunteers – developed a test suite
that implementors would test against while there still was time to
fix the problems. Todd Fahrner created the
acid test in
October 1998, which
became the ultimate challenge. See Figure 3.
When a test suite is available, someone must do the testing.
Brian Wilson has done a remarkable job of testing CSS
implementations and making the results available on the Web.
We should also mention the work in more recent years of Gérard
Talbot and Geoffrey Sneddon on the official CSS testuite. And of
course of Peter Linss, whose Shepherd server is a great help in
seeing what tests exist, running them, and generating reports of
Without compelling content, CSS hasn't served its purpose. Dave
Shea created the CSS Zen
garden to show fellow graphics artists why CSS should be taken
seriously. He, along with the many people who created submissions,
showed people how to use CSS creatively.
The Web has been trapped on the desktop for too long. Making it
available on mobile phones is one important escape. Michael Day
and Xuehong Liu have shown us another way out: The Prince
formatter converts HTML and XML documents to PDF and is entirely
based on CSS. This product enabled Håkon and Bert to abandon
traditional word processors and use Web standards. Their book was written entirely in HTML
CSS level 2 contained a feature called
i.e., the ability to embed fonts in a Web document. The idea was
that a designer who wanted a specific font could actually provide
the font along with the style sheet. During ten years, only
Microsoft's Internet Explorer browser implemented that feature.
(Netscape for a short period implemented an alternative, which
didn't use CSS, wasn't as good, and was probably illegal in many
countries because it slightly changed how each font looked.)
The reason Web Fonts didn't get implemented was twofold. First
of all there were few fonts whose copyright allowed them to be
distributed. Most fonts could be used to print documents locally,
but you weren't allowed to put them on the Web.
Secondly, Microsoft and Monotype had developed a format called
EOT (Embedded OpenType), which contained inside the fonts the
names (URLs) of the documents that could be rendered with them.
This allowed an EOT font to be made available on the Web alongside
a document, because it now couldn't be used for any other
document. But, the format was proprietary and nobody else but
Microsoft could use it.
All that changed in early 2008. By then there were many more
free fonts, i.e., fonts whose designers allowed them to be
distributed for free on the Web. Håkon therefore started lobbying
browser makers to finally implement Web Fonts (for fonts in the
standard TrueType and OpenType formats) and Bert asked Microsoft
if they couldn't open up EOT, so that others could implement it,
too. In May, Microsoft and Monotype submitted EOT to W3C
under a royalty-free license. And browsers started implementing
support for downloading TrueType and OpenType fonts.
After further discussion, however, most browser makers decided
not to implement EOT, but ask W3C to develop a new font format
instead. The reason was that that they preferred to use the gzip
compression algorithm (which was already used for HTTP) rather
than add new code for the MicroType Express algorithm used by EOT.
That new format became WOFF.
Rather than embed the URL of a document in the font, it relies on
an HTTP feature (the
origin header), which allows to give
the domain part of a document's URL: less precise than a full URL,
but still good enough for most font makers.
In the end, however, WOFF still adopted parts of EOT's MicroType
Express algorithm, and a new compression algorithm (Brotli),
because it allowed better compression than gzip.
Web Fonts have become very popular. Free fonts are used directly
in the TrueType or OpenType format in which they were made. Less
free fonts use the WOFF and EOT formats.
There are now online services where you can find and download
fonts (both free and non-free). And some even offer to host the
fonts on their servers. In some cases even for free. (Which means
they provide bandwidth, but in return they gather statistics on
New directions: books and GUIs
The development of CSS hasn't stopped. Far from it. CSS now has
more than 60 modules that define different capabilities, some
already part of the standard, some still in development.
It is now common that books are made with CSS. Not all books,
though, because CSS is still missing features for the more complex
layouts. That is one direction in which the language is being
E-books also use CSS, which requires yet other features. EPUB is
the most widely implemented format for e-books. It was developed
by IDPF. IDPF and W3C are currently (December 2016) in the
process of merging their operations. The next EPUB version should
then be made at W3C and the development of CSS features for books
and e-books will be easier.
The development of programs (
apps) that use graphical
user interfaces made out of HTML and CSS has also put new demands
on CSS. Some of the latest modules of CSS deal with layout of user
interfaces rather than documents. Although: as they are part of
the same CSS, nothing prohibits their use for documents, too, if a
part of a document happens to have a mark-up structure that allows
Over time, some browsers and other implementations have
disappeared, and new ones have been created. There are now also
languages derived from CSS for other purposes than styling
documents. Probably the first language that used the syntax of CSS
(but not the cascading and inheritance model) was STTS, by Daniel Glazman. That was in 1998. Since then others
have made their appearance. Three that are currently in use are Qt Style
Sheets for styling widgets in the Qt GUI toolkit, JavaFX Style Sheets, which does the same for the JavaFX UI
widgets of Java, and MapCSS for
describing the style of maps.
It is difficult to count how widely CSS is used, but the number
of HTML pages that does not use CSS is probably not more
than a few percent. Many people make their living as CSS designers
or from CSS conferences. And the number of books written about CSS
can no longer be counted.
Some day CSS will be replaced by something else. But before
that, CSS will have time to celebrate its 21st birthday…