Its a bad news for all Yahoo Publisher (YPN), they are closing its advertisement network. YPN is similar to Google adsense and helped many website owners in their earning but not very popular because of its some restrictions.
It is closing on April 30th 2010. There Ad network was made for USA users only and it is still in beta. Yahoo has recently sent emails to all their publishers and asked them to remove Ad code from their site. But they have also recommended Chitika as an alternative advertiser in their mail.
Original text
dear publisher,
yahoo! Continuously evaluates and prioritizes our products and services, in alignment with business goals and our continued commitment to deliver the best consumer and advertiser experiences. After conducting an extensive review of the yahoo! Publisher network beta program, we have decided to close the program effective april 30, 2010…….
Chitika has already created separate sign up page for YPN beta users. Don’t worry about the payments, they will be sent them by the end of April month.
I thought they will recommend Microsoft Pub Center beta program since they are partners. Anyway I am sure this decision will not affect many webmasters since they had a very small share.
Yahoo is closing many of their services. Looks like they facing the heat of the competition with Google.

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YPN was not likely to last long because it was exclusive to US publishers only. Compared it to Google that covers most countries in world, YPN was a case of online isolation.