The on-again, off-again relationship between Microsoft and Yahoo appears to have heated up once more, as it emerged over the weekend that the two firms have been in renewed talks.

Typically unconfirmed, the rumours say that Microsoft's Steve Ballmer met recently with Yahoo CEO Carol Bartz to discuss cooperation on search and advertising. Neither has spoken publically about the alleged meeting.

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The story has it that Yahoo could end up running the display advertising business of both companies, while Microsoft looks after the advertising served up with search results, both traditional Google strong suits.

While there's still nothing more than chatter to the suggestions, Ballmer did stoke the 'Microhoo' fire last week, saying: "Unless I'm fooling myself, over time I would expect there's a good opportunity for a deal."