Yahoo has launched its digital advertising solution called APT (formerly called AMP).

An excerpt from Search Engine Journal

Specifically, these benefits are:

Fostering a more transparent marketplace through the ability to connect to new business partners for cross-selling;
Providing ad selection and inventory management tools to match relevant ads to marketers' target audience; and
Allowing publishers to manage their own private networks.

Yahoo is fighting hard to defend its teaming up with Google for serving text ads beside Yahoo results. While that stays, display ads is one area where Google has relatively lesser market share.

Supposing that Yahoo does real well with the display ads solution, would it still be able to challenge Google in the long run? That is a question that most have on their mind. This only leaves Microsoft as a eligible competitor to Google and that too a very distant one.