A federal judge has upheld a jury ruling that Microsoft's Internet Explorer (IE) Web browser infringed on a patent owned by Eolas Technologies and the University of California, and ordered the company to pay $520.6 million in damages.

Judge James B Zagel issued the order in the US District Court for the Northern District of Illinois, reaffirming a jury decision reached last August. He also denied Microsoft's motion to suspend a decision until the US Patent and Trademark Office (PTO) completes a reexamination of the patent, number 5,838,906 (or '906), which it launched last November.

A spokeswoman for Microsoft in the UK said that the Redmond, Washington, company would appeal the case, most likely within the next 30 days.

Though the judge barred Microsoft from distributing versions of IE that include the potentially infringing technology, he also held the injunction until an appeal has run its course.

"We feel good about our prospects on appeal, remain steadfast in our belief that the Eolas patent is not valid and are heartened by the PTO's review of the patent," the spokeswoman said. "While the judge did not grant all of our post-trial motions, we are pleased the court accepted some of our arguments and decided to stay the injunction pending our appeal."

Representatives from Eolas; its Minneapolis law firm, Robins, Kaplan, Miller & Ciresi LLP; the University of California and the US District Court for the Northern District of Illinois could not immediately be reached for comment.

The technology covered in the '906 patent was developed by Eolas president Michael Doyle at the University of California at San Francisco. The patent describes in part "a system allowing a user of a browser program… to access and execute an embedded program object," or small computer programs, often referred to as "applets" or "plug-ins." Eolas, which stands for "Embedded Objects Linked Across Systems," jointly holds the patent with the University of California.