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Håkon Wium Lie

Summary

Håkon Wium Lie (born 1965) is a Norwegian computer scientist who proposed Cascading Style Sheets (CSS) on October 10, 1994, while working at CERN. With Bert Bos he wrote CSS level 1, a W3C Recommendation of December 17, 1996. He was chief technology officer of Opera Software from 1999 to 2016, came up with the Acid2 browser test in 2005 and defended a PhD thesis on CSS at the University of Oslo in 2006.

Web Building Encyclopedia · People · Last reviewed October 22, 2026 · 11 min read

Early life and education

Håkon Wium Lie was born on July 26, 1965, in Halden, Norway.1 He studied computer science at Østfold College from 1984 to 1986, then completed a bachelor of science in computer science at West Georgia College in the United States in 1987.1

His first jobs were at the OECD Halden Reactor Project and at Norwegian Telecom Research, where he programmed a desktop manager under Unix and X11.1 In the summer of 1990 he was a summer student in the OpenWindows group at Sun Microsystems in Mountain View, California.1

From 1989 to 1991 he studied at the Massachusetts Institute of Technology (MIT), earning a master of science in visual studies. As a research assistant at the MIT Media Lab he worked in Walter Bender’s Electronic Publishing group, and his master’s thesis was titled “The Electronic Broadsheet.”1

In the MIT Media Lab’s profile of him, Lie says the CSS specification is deeply influenced by what he learned there.2 His later PhD thesis makes the same point, saying CSS borrowed many ideas from the lab.3 After MIT he returned to Norwegian Telecom Research as a research scientist from 1991 to 1994.1

At CERN: the 1994 proposal

In 1994 Lie moved to CERN, the physics laboratory near Geneva where the World Wide Web began. His CV describes him as a scientific associate on the WWW project under Tim Berners-Lee, where he co-developed Arena, a testbed browser for HTML3, and was technical coordinator of the CERN WWW development team.1

Arena had been started by Dave Raggett, and Lie’s thesis calls it the perfect testing ground for style sheets.3 In a 2008 interview Lie said he proposed style sheets because he felt layout, typography and aesthetics were missing from the early web.4

On October 10, 1994, he published “Cascading HTML style sheets: a proposal.” The page is marked version 0.92, calls itself work in progress and gives a contact address at info.cern.ch.5 A style sheet is a separate set of rules that tells a browser how to display a document, such as which font or size to use for headings.

The proposal described a simple mapping between HTML elements and presentation hints. Its key idea was the cascade: the reader’s browser sets its own preferences first and “hands the remaining influence over to the style sheets referenced in the incoming document.”5 It covered non-visual media such as speech and braille as well as screens and paper.5 Its acknowledgments thank Berners-Lee, Raggett and Phill Hallam-Baker.5

Lie later noted that the proposal appeared three days before Netscape announced its first beta browser on October 13, 1994.3 How the proposal worked, and how it grew into today’s styling language, is covered in our entry on CSS.

Bert Bos’s history of CSS says the first proposal was presented at the web conference in Chicago, which it dates to November 1994.6 The published agenda of that meeting, the Second International World Wide Web Conference, gives its dates as October 18 to 20, 1994, with tutorials on October 17.7 The agenda lists him, spelled Haakon Lie and identified with CERN, in a technical session on HTML and SGML on October 20, though it does not mention style sheets by name.7

Building CSS at the W3C

At about the same time Bert Bos was building Argo, a highly customizable browser with style sheets, and he decided to join forces with Lie.6 At the Third International WWW Conference in Darmstadt, Germany, held April 10 to 14, 1995, Lie showed a version of Arena modified to support CSS.6 The www-style mailing list for discussing style sheets was created in May 1995.6

By 1995 Lie and Bos were based in Sophia-Antipolis in southern France, where the World Wide Web Consortium (W3C), the body that sets web standards, had set up its European site.6 Lie’s CV says he was the first W3C employee there, at the French research institute INRIA, and that he coordinated the technical team and served as the W3C’s area leader for style sheets.1

His thesis describes a few weeks in the summer of 1995 when he and Bos, working around a whiteboard in Sophia-Antipolis, turned immature ideas into a coherent draft. The draft was declared stable in December 1995, and browser makers were encouraged to implement it.3

In April 1996 Lie presented CSS to the W3C’s HTML Editorial Review Board and took the minutes. According to his thesis, that is the meeting where the name HTML 3.2 was chosen.3

CSS level 1 became a W3C Recommendation, the consortium’s word for a finished standard, on December 17, 1996. The specification lists two authors, Lie and Bos.8 It describes a simple mechanism for attaching styles such as fonts, colors and spacing to HTML documents, with author and reader style sheets combined by the cascade.8

CSS level 2 followed on May 12, 1998, edited by Bos, Lie, Chris Lilley and Ian Jacobs. It added style sheets for specific media such as printers and braille devices, positioning of content, downloadable fonts and table layout.9

Lie and Bos also wrote a book about the language, Cascading Style Sheets: Designing for the Web. Its third edition was published by Addison-Wesley on April 25, 2005.10

Chief technology officer of Opera

On April 13, 1999, Opera Software announced that Lie had joined the Oslo company as chief technology officer (CTO), the executive responsible for its technology. He left his post as the W3C’s activity lead for style sheets but stayed involved in the consortium as Opera’s member representative.11

The announcement quoted his reasoning: “It’s important for the Web and W3C that there is more than one browser.” He warned that a vendor dominating the browser market would in effect decide which W3C standards were used.11 His thesis says he joined Opera to make sure at least one browser implemented the CSS specifications correctly.3

Opera had already moved in that direction. Bos’s history records that Opera 3.5, released in November 1998, supported most of CSS1, and that Lie was so impressed with Opera’s technology that he joined as CTO in 1999.6 The same year, MIT Technology Review named Lie to its list of innovators under 35, citing the CSS proposal and his work setting up the W3C’s technical team in France.12

He kept editing standards from Opera. When the revised CSS 2.1 became a W3C Recommendation on June 7, 2011, its four editors were Bos, Tantek Çelik, Ian Hickson and Lie, listed with an opera.com address.13 In 2010 he described himself as representing Opera in both the CSS and Web Fonts working groups.14

Sources differ on when the role began. Opera’s 1999 announcement and his W3C home page say he joined in April 1999,1115 while the MIT Media Lab profile says he was CTO from 1998 until 2016.2 His own site gives 1999 to 2016 and says his time ended when the browser was sold to a Chinese consortium. The last project he worked on there was Opera Neon, a concept browser.16

The Acid2 and Acid3 tests

An acid test, in web terms, is a test page that checks a browser’s support for several web standards at once, so that flaws are quickly exposed.1718 The first one was not Lie’s, and sources give different years for it. Bos’s history credits Todd Fahrner with creating the acid test in October 1998.6 The Web Standards Project (WaSP) wrote in 2005 that a group called the CSS Samurai launched the Acid Test in 1997, and in 2008 it credited Fahrner with creating that 1997 test with the CSS Samurai.1819

In March 2005, while Microsoft was developing Internet Explorer 7, Lie published a column on CNET’s News.com titled “The Acid2 Challenge to Microsoft.” WaSP announced on March 16, 2005 that Lie and WaSP had begun developing the Acid2 test to encourage Microsoft to add as much CSS 2 support as possible.20

The framing drew criticism. In a blog post a week later, the CSS writer Eric Meyer asked why the challenge was aimed only at Microsoft.21 WaSP explained that Lie had asked it to host the test, and that its role was to help build, publish and promote a test of CSS 2.1 support for all browsers.22

WaSP released Acid2 on April 13, 2005. It was designed to test HTML, CSS and PNG image support in browsers and authoring tools, and Apple’s Dave Hyatt said that day that he had started work on making Safari pass it.18 A browser that passed drew a simple smiling face.4

Lie later described the division of work. “The idea for Acid2 was mine,” he said in 2008, adding that Ian Hickson wrote the test code. The smiley was chosen because people recognize it instantly and can see when something is wrong.4

WaSP’s Acid2 page records that Opera 9 passed the test, in a note dated July 20, 2006, and that Internet Explorer 8 passed on December 19, 2007.17 The story belongs to the wider browser wars over standards support.

A third test followed. WaSP released Acid3 on March 3, 2008, as a set of 100 mini-tests aimed mainly at DOM scripting, the combination of ECMAScript (the standard behind JavaScript) and the W3C Document Object Model that interactive web applications rely on.19 Its list of tested specifications also includes CSS2 web fonts through @font-face.23 WaSP’s announcement credits no individual author, and neither it nor WaSP’s Acid3 page names Lie.19 On December 4, 2008, Opera said the alpha version of Opera 10 scored 100 out of 100 on Acid3.24

Web fonts and print CSS

Web fonts

Web fonts are font files that a page downloads, so text can appear in a typeface the visitor does not have installed. CSS2 already described a way to link to fonts in 1998. Lie wrote in 2007 that Microsoft and Netscape each picked a different, little-used font format with few tools to support it (EOT and TrueDoc), and that web fonts then disappeared from designers’ toolboxes.25

In “CSS @ Ten: The Next Big Thing,” published by A List Apart on August 28, 2007, he argued that designers should be able to link to real TrueType font files with the @font-face rule. “Instead of making pictures of fonts, the actual font files can be linked to and retrieved from the web,” he wrote.25 At the time, the article said, the only program that supported TrueType web fonts was Prince, a document formatter.25 The same day he proposed a new media query on the www-style list, so a style sheet could test whether web fonts were available.26

Bos’s history says Lie started lobbying browser makers in 2008 to implement web fonts at last.6 In May 2008 Lie said one of Opera’s developers had recently added web font support.4 That month, Microsoft and Monotype submitted EOT to the W3C, but most browser makers preferred a new format, WOFF.6

When the W3C’s Web Fonts Working Group formed, Lie introduced himself on its list in April 2010. He said earlier efforts had failed mainly because browser makers never agreed on a common font format.14 WOFF File Format 1.0, written by Jonathan Kew, Tal Leming and Erik van Blokland, became a W3C Recommendation on December 13, 2012.27

Print, paged media and columns

Lie has long worked on CSS for printed output. He is chairman of YesLogic, the company that makes Prince, which converts web content to PDF using CSS.216 Bos describes Prince as entirely based on CSS, and says it let him and Lie abandon traditional word processors and use web standards.6 Lie’s site says their CSS book was written in HTML and CSS and converted to PDF with Prince.16

On November 28, 2005, Lie and Bos published an A List Apart article on printing a book with CSS. It introduced boom, a set of HTML class names they developed for marking up chapters, sidebars and figures, and showed CSS rules for page sizes, running headers, page numbers and cross-references that print the page number of the section they point to.28 Some of those features came from CSS2 and others from drafts for CSS3.28

He edited several of the specifications behind these features. The multi-column layout module, which flows text into newspaper-style columns, was first published as a W3C draft on June 23, 1999.29 The January 18, 2001 draft names Lie of Opera Software as its editor,30 and he was still the sole editor of the April 12, 2011 Candidate Recommendation.31 The current version, dated May 16, 2024, is edited by Florian Rivoal and Rachel Andrew and lists Lie as a former editor.32

He is also listed as a former editor of the CSS Paged Media module, which covers page size, margins and headers,33 and of the CSS Generated Content for Paged Media module, which covers running headers and footers, footnotes and page selection.34 In January 2014 he argued against a competing layout proposal, CSS Regions, recommending multi-column layout and CSS Figures, a set of extensions for floats and column spanning, instead.35

The PhD thesis on CSS

Lie began writing a doctoral thesis in 2001, with help from Ole Hanseth and Gisle Hannemyr.16 Titled simply “Cascading Style Sheets,” it was submitted to the Faculty of Mathematics and Natural Sciences at the University of Oslo on March 29, 2005.3

He announced on February 16, 2006 that he was defending the thesis that day and the next.36 Its abstract opens: “The topic of this thesis is style sheet languages for structured documents on the web.”3

The thesis argues that the web, with its many output devices and reader preferences, needs different style sheet languages than traditional electronic publishing. It analyzes style sheet languages from before the web and proposals made for the web from 1993 to 1996, then describes the design of CSS.363

It also serves as a first-hand record of how CSS was made, from the 1994 proposal to the CSS2 Recommendation of May 1998.3 In a 2008 interview Lie said the comparison showed that CSS had missed some good ideas from that earlier period.4

Timeline

  1. His time as Opera's chief technology officer ends16
  2. Argues against CSS Regions in A List Apart, favoring multi-column layout35
  3. CSS 2.1, with Lie among its four editors, becomes a W3C Recommendation13
  4. Opera says the Opera 10 alpha scores 100 out of 100 on Acid324
  5. Publishes "CSS @ Ten: The Next Big Thing" on TrueType web fonts25
  6. Begins defending his PhD thesis on CSS at the University of Oslo36
  7. Publishes an A List Apart article on printing a book with CSS, with Bert Bos28
  8. The Web Standards Project releases the Acid2 test18
  9. WaSP announces that Lie and WaSP are developing Acid220
  10. Multi-column layout draft published with Lie as editor30
  11. Opera Software announces Lie as its chief technology officer11
  12. CSS level 2, co-edited by Lie, becomes a W3C Recommendation9
  13. CSS level 1, by Lie and Bert Bos, becomes a W3C Recommendation8
  14. Publishes "Cascading HTML style sheets: a proposal" while at CERN5
  15. Born in Halden, Norway1

What it means for your website

Lie’s work explains several things you can use on any site today, whether you build it yourself or use a builder.

  • Keep content and style apart. His proposal put presentation in separate style sheets that a document refers to, instead of in the HTML itself.5 Website builders and WordPress themes do the same: when you change a font or color in the theme settings, it changes everywhere. Our page on templates and themes explains what moves with your content if you switch.
  • Give your pages a print style sheet. Menus, price lists and directions still get printed. A few rules inside @media print can hide navigation and footers, and @page sets paper margins.37 Use your browser’s print preview to check.
  • Serve web fonts the modern way. MDN recommends WOFF2 files for @font-face because they compress better than older formats, and notes that font files must come from the same domain as the page unless the server allows otherwise.38 WOFF is meant for properly licensed fonts,27 so check that your font license covers web use. Fonts are one of the items on our website ownership checklist.
  • Let columns adapt. Multi-column layout has worked across browsers since March 2017.39 A rule such as columns: 20em lets the browser pick the number of columns for the screen width,35 which suits responsive design.
  • Test in more than one browser. The Acid tests showed that browsers can read the same code differently.18 Before launch, open your site in Chrome, Safari and Firefox and on a phone.

See also

References

  1. Curriculum Vitae: Håkon Wium Lie. Håkon Wium Lie, W3C. accessed October 22, 2026.
  2. Håkon Wium Lie: overview. MIT Media Lab. accessed October 22, 2026.
  3. Cascading Style Sheets (PhD thesis). Håkon Wium Lie, Faculty of Mathematics and Natural Sciences, University of Oslo. 2005-03-29. accessed October 22, 2026.
  4. Håkon Wium Lie: CSS was created to save HTML. Martin Hassman, Root.cz. 2008-05-12. accessed October 22, 2026.
  5. Cascading HTML style sheets: a proposal. Håkon W Lie, hosted by W3C. 1994-10-10. accessed October 22, 2026.
  6. A brief history of CSS until 2016. Bert Bos, W3C. 2016-12-17. accessed October 22, 2026.
  7. The agenda for the Second International World Wide Web (WWW) Conference. IW3C2 archives. 1994-10. accessed October 22, 2026.
  8. Cascading Style Sheets, level 1 (W3C Recommendation). W3C (Håkon Wium Lie, Bert Bos). 1996-12-17. accessed October 22, 2026.
  9. Cascading Style Sheets, level 2: CSS2 Specification (W3C Recommendation). W3C (Bert Bos, Håkon Wium Lie, Chris Lilley, Ian Jacobs). 1998-05-12. accessed October 22, 2026.
  10. Cascading Style Sheets: Designing for the Web, 3rd Edition. Addison-Wesley Professional, InformIT. 2005-04-25. accessed October 22, 2026.
  11. W3C's Hakon Wium Lie Joins Opera as Chief Technology Officer. Opera Software. 1999-04-13. accessed October 22, 2026.
  12. Håkon Wium Lie, Innovators Under 35, 1999. MIT Technology Review. 1999. accessed October 22, 2026.
  13. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. W3C (Bert Bos, Tantek Çelik, Ian Hickson, Håkon Wium Lie). 2011-06-07. accessed October 22, 2026.
  14. Re: Welcome, and introductions. Håkon Wium Lie, public-webfonts-wg mailing list, W3C. 2010-04-12. accessed October 22, 2026.
  15. Håkon Wium Lie. W3C. accessed October 22, 2026.
  16. Håkon Wium Lie. Håkon Wium Lie, wiumlie.no. accessed October 22, 2026.
  17. Acid2. The Web Standards Project. accessed October 22, 2026.
  18. Acid2: Putting Browser Makers on Notice. Drew McLellan, The Web Standards Project. 2005-04-13. accessed October 22, 2026.
  19. Acid3: Putting Browser Makers on Notice, Again. The Web Standards Project. 2008-03-03. accessed October 22, 2026.
  20. The Acid2 Challenge. Molly E. Holzschlag, The Web Standards Project. 2005-03-16. accessed October 22, 2026.
  21. That Acid Buzz. Eric A. Meyer, meyerweb.com. 2005-03-23. accessed October 22, 2026.
  22. Interview with Håkon Wium Lie. Molly E. Holzschlag, The Web Standards Project. 2005-03-31. accessed October 22, 2026.
  23. Acid3. The Web Standards Project. accessed October 22, 2026.
  24. Opera 10 sneak peek. Opera Software. 2008-12-04. accessed October 22, 2026.
  25. CSS @ Ten: The Next Big Thing. Håkon Wium Lie, A List Apart. 2007-08-28. accessed October 22, 2026.
  26. The Next Big Thing. Håkon Wium Lie, www-style mailing list, W3C. 2007-08-28. accessed October 22, 2026.
  27. WOFF File Format 1.0 (W3C Recommendation). W3C (Jonathan Kew, Tal Leming, Erik van Blokland). 2012-12-13. accessed October 22, 2026.
  28. Printing a Book with CSS: Boom. Håkon Wium Lie and Bert Bos, A List Apart. 2005-11-28. accessed October 22, 2026.
  29. CSS Multi-column Layout Module Level 1: publication history. W3C. accessed October 22, 2026.
  30. CSS3 module: Multi-column layout (W3C Working Draft). W3C (Håkon Wium Lie). 2001-01-18. accessed October 22, 2026.
  31. CSS Multi-column Layout Module (W3C Candidate Recommendation). W3C (Håkon Wium Lie). 2011-04-12. accessed October 22, 2026.
  32. CSS Multi-column Layout Module Level 1. W3C (Florian Rivoal, Rachel Andrew). 2024-05-16. accessed October 22, 2026.
  33. CSS Paged Media Module Level 3. W3C (Elika J. Etemad). 2023-09-14. accessed October 22, 2026.
  34. CSS Generated Content for Paged Media Module. W3C (Mike Bremford, Rachel Andrew). 2024-01-25. accessed October 22, 2026.
  35. CSS Regions Considered Harmful. Håkon Wium Lie, A List Apart. 2014-01-22. accessed October 22, 2026.
  36. PhD thesis on style sheets. Håkon Wium Lie, www-style mailing list, W3C. 2006-02-16. accessed October 22, 2026.
  37. Printing. MDN Web Docs, Mozilla. accessed October 22, 2026.
  38. @font-face. MDN Web Docs, Mozilla. accessed October 22, 2026.
  39. columns. MDN Web Docs, Mozilla. accessed October 22, 2026.

Web Building Encyclopedia. First published October 22, 2026. Last reviewed October 22, 2026. Every fact on this page is linked to a source we opened. Spotted an error? Write to [email protected].