Yahoo is reportedly testing a new contextual advertising program to compete with Google’s Adsense program. Rumors had started when Overture product manager Ken Rudman placed contextual ads on his own blog. Investment firm UBS even upgraded Yahoo’s stock to a “buy” rating based in part on expectations the portal giant will increase its Content Match product exposure. Currently, that contextual network remains available only to very large publishers. Raining on the parade, Jupiter Research’s seldom sanguine Niki Scevak said that Adsense hasn’t appeared to have done much for Google, and less might be expected from a similar entry by Yahoo.