Internet Explorer and Apple's Webkit rendering engine (also used in Google Chrome) may one day unite, hinted Microsoft CEO Steve Ballmer at a recent developer conference.

Ballmer began his answer philosophically, saying Microsoft will need to look at what the browser is like in the future and, if there is no innovation around them, which he thinks is "likely", Microsoft may still need its own browser because of proprietary extensions that broaden its functionality.

"There will still be a lot of proprietary innovation in the browser itself so we may need to have a rendering service," he said.

Then came the startling revelation that Microsoft may also adopt an open source browser engine.

"Open source is interesting," he said. "Apple has embraced Webkit and we may look at that, but we will continue to build extensions for IE 8."

Ballmer also admitted Microsoft got delayed with the transition from IE 6 to IE7 during the development of Longhorn, which became Vista. "But I don't what to go there."