"A lot of big advances will underlie this new class of applications," Gates predicted in his final keynote as chairman of Microsoft. "You will take [services] for granted."
Gates highlighted many of his company's newest web-based offerings during the keynote, include photo-sharing and invitation services.
He also announced a major win for Microsoft's Silverlight web-app development system. The software will be deployed by NBC this summer to provide more than 3,000 hours of online video coverage of the Olympics in Beijing.
Microsoft's Zune portable media player will also play a prominent role in the company's web services plans.
Users will be offered a new 'Zune Card' service to automatically update a list of recent and most-played songs to a web page that can be shared with friends.
Microsoft hopes that the new services will give Zune a better foothold in a market dominated by Apple.
"I think it is quite clear that [Zune] is becoming the clear alternative to the iPod," said Robbie Bach, president of Microsoft's entertainment and devices division.
The company has also inked a deal with BT to offer a set-top box bundled with Microsoft's Mediaroom television service.
Microsoft also showcased new mobile services. Bach demonstrated the Tellme voice-command service, while Gates showed a prototype mobile service in which users and locations could be recognised and used with other services, such as maps and calendars.
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