Microsoft has lost a patent infringement battle over its wrongful use of a key web browsing technology.
The US patent office has upheld the validity of a patent held by the University of California and its Eolas Technology spin-off company.
In 2003, a jury awarded more than $500m (£295m) in damages to the university and Eolas for Microsoft’s infringement of the technology.
Microsoft appealed and won the right to try to prove that similar technology existed ahead of Eolas’ patent application.
The University of California said the patent office’s ruling meant that Microsoft’s claims that the Eolas patent was invalid had been shown to be false.
Microsoft said it was “disappointed” at the ruling, but would still be following through with its forthcoming court action to pursue its claims.