Håkon Wium Lie (born July 26, 1965) is a Norwegian web pioneer, a standards activist, and the Chief Technology Officer of Opera Software from 1998 until the browser was sold to new owners in 2016. He is best known for developing Cascading Style Sheets (CSS) while working with Tim Berners-Lee and Robert Cailliau at CERN in 1994. Education and career Håkon Wium Lie attended Østfold University College, West Georgia College, and MIT Media Lab, receiving an MS in Visual Studies in 1991. On February 17, 2006, he successfully defended his PhD thesis at the University of Oslo. His PhD thesis is background to the origins of CSS and a rationale to some of the design decisions behind it – particularly as to why some features were not included and why CSS avoids trying to become DSSSL. He has worked for, among others, the W3C, INRIA, CERN, MIT Media Lab, and Norwegian telecom research in Televerket. Web Standards While working with Tim Berners-Lee and Robert Cailliau at CERN in 1994, he proposed the concept of Cascading Style Sheets (CSS). As a showcase and testbed, he integrated CSS into the Arena web browser, which became the first CSS implementation. After joining W3C in 1995, he worked on the CSS specifications, including CSS1, CSS2, and RFC 2318 (March 1998). Most of these specifications were developed with Bert Bos, who is considered co-creator of CSS. Over the next decade, CSS established itself as one of the fundamental web standards, with profound impact on typography, aesthetics, and accessibility on the web. Along with his work on the CSS specifications, Wium Lie has been an activist for standards in general. In 2005, he wrote an open letter to Bill Gates of Microsoft, asking why Microsoft's Internet Explorer did not support common web standards. A few days later, when Bill Gates announced that Internet Explorer 7 would be launched, Wium Lie responded by launching the Acid2 challenge to Microsoft. Although primarily targeted at Microsoft, the Acid2 test was also difficult for other browsers. Since then, Acid2 and the subsequent Acid3 have established themselves as benchmark tests which all browsers are measured against. In 2006, Wium Lie started campaigning for browsers to support downloadable web fonts using common font formats. , all major browser vendors have implemented web fonts this way. In 2007, Wium Lie started campaigning for the video element to make it easier to publish video