Marketing moment 'Anti-Google' alliance.

- What has happened?

Executives from AOL, Yahoo! and Microsoft are reported to have met in New York last week to discuss a pact to sell one another's ad inventory Such a move would challenge Google's dominance of the ad sales market.

While the companies have neither confirmed nor denied the report, they have released strikingly similar statements about how they have 'existing relationships' and are 'looking at new ways' to expand them.

- How would it work?

All three digital companies would sell one another's unsold 'class 2 inventory' ads, which are normally handed over to ad networks. They would then split the revenue three ways.

It is …