You site should be popular and of high traffic and you must from US or canada.If your satisfy those terms,get details here http://advertisingcentral.yahoo.com/publisher/index
Its a pity that they are not allowing sites from other countries, may be because they don't have that much of advertisers!!!
If you are from US or Canada, then apply. They will evaluate your site and then based on their decision it goes forward
Yup, not for every country. They have limits and they dont need as many publishers as google does. Google is a king over the internet.
is that possible i m from usa and my working team of website from other countries and also my site is not popular in usa but in other countries its popular than i m able to use thi sor not
Yes , Yahoo offers adds like goggle , that is YPN , but its very low costs and also i am not sure wheter it actually exist now.