The most important patent case in the history of the Internet, Eolas vs. Microsoft, reached another milestone last November when the U.S. Patent and Trademark Office (USPTO) ordered a rare reexamination of Eolas's patent, which gives the one-person company control of a key Web browser technology.

Patent No. 5838906 had already made headlines last August as the basis of a US $521 million jury award in an infringement lawsuit that pitted Eolas Technologies Inc., in Chicago, against the mighty Microsoft Corp., in Redmond, Wash. Eolas argued, successfully, that Microsoft's Internet Explorer browser (and, in fact, all browsers) infringe its patent in the way that it invokes other software, such as a media player, to display a document that incorporates sounds, graphics, or video clips. Microsoft has said it will appeal. In the meantime, it is awaiting a decision on several post-trial motions that are to be ruled on by 6 January.

Microsoft will not be proceeding on its own. In October, Tim Berners-Lee, inventor of the Web and head of the World Wide Web Consortium (W3C), in Cambridge, Mass., wrote a letter to the patent office asking that it reconsider the patent in order to "prevent substantial...damage to the World Wide Web" [see "David and Goliath Versus Another David," IEEE Spectrum, December 2003]. Berners-Lee said that the original patent examination, despite taking more than three years, failed to sufficiently consider earlier software, which if they predate the patent and do the same things, undermine a patent's claim to originality. The existence of so-called prior art, in other words, invalidates an invention's right to be patented.

It seems almost inconceivable that the question of prior art for the '906 patent wasn't sufficiently vetted between 1994, when the patent application was filed, and 1998, when it was granted, or between 1999, when Eolas filed suit against Microsoft, and last summer, when the jury arrived at its verdict after a five-week trial. But, according to Terry Carroll, an intellectual property attorney in Santa Clara, Calif., "a grass-roots effort can unearth more prior art than was available in the original patent examination." In his letter, Berners-Lee asks the patent office to look at two publications that he says show prior art "never considered by the [USPTO] during the prosecution of the '906 patent."

The two documents relate to a software specification called HTML+, which was written by Dave Raggett, at the time a researcher at Hewlett-Packard Laboratories, and now a researcher at Berners-Lee's organization, the W3C. HTML+ was an extension of the earliest version of HTML, the Web's coding system for documents that tells a browser how to display, and to link to, other Web documents.

In 1993, Raggett participated on a mailing list, www-talk, devoted to early Web browser software. Among the features discussed on the list, and subsequently included in HTML+, was a tag called EMBED. The tag, says Berners-Lee, "is identical in all material respects to the EMBED tag described in the Eolas '906 patent, which in turn was the basis for its claims."

Raggett told Spectrum that although he was a witness at last summer's trial, the evidence he gave "was not part of the ruling." He testified for less than a hour, and the questioning covered only a small part of his work.

Raggett thinks that many other examples of prior art may not have been fully considered by the patent office. He mentioned Microsoft's own object linking and embedding technology, Apple's Hypercard, Asymetrix Toolbook, and the NeXT operating system.

Richard Smith, an Internet journalist in Cambridge, Mass., who maintains a Web page on the '906 patent (http://www.computerbytesman.com/906patent/) , also thinks there's "a lot of fertile ground to look around for prior art," including early versions of Lotus Notes, the Unix Xwindows system, and bulletin-board software of the 1980s and early 1990s.

Eolas's lead attorney, Martin Lueck, a partner in the Minneapolis law firm Robins Kaplan, Miller and Ciresi LLP, disagrees. "It's not as simple as it seems," he says. "The question of prior art here really requires a detailed level of analysis. If you look at when the Web started, this invention is incredibly early. That's the reason we won at trial."

The jury has long since gone home, but the trial is not quite over. Microsoft has filed a number of motions that preserve its rights in its promised appeal. In a brief 4 December hearing, Judge James B. Zagel said he would rule on them by 6 January. The entire appeals process is expected to take another year. Now, though, Eolas has to beat not just Microsoft, but the entire Web busily scanning its own history for prior art.