Some advertisers offer multi-tier programs that distribute commission into a hierarchical referral network of sign-ups and sub-partners. In practical terms, publisher "A" signs up to the program with an advertiser and gets rewarded for the agreed activity conducted by a referred visitor. If publisher "A" attracts publishers "B" and "C" to sign up for the same program using his sign-up code, all future activities performed by publishers "B" and "C" will result in additional commission (at a lower rate) for publisher "A".
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I do have a question, though, you state that longer articles are better (which I understand). I've found a niche that has a few keywords with very high CPC (no real affiliation program can be used though), with a few thousand searches a month. For each keyword I could probably 500 words on each keyword. Should I do this, or should I compile them into one big article? They keywords can be linked to each other, for example, "how to start running", "basics of running" etc. (Those obviously aren't the keywords, and more can be written on those). What would you recommend?

This is the most popular payment offered by most of the affiliate programs. Under this program, the affiliate marketers earn commissions from the merchant each time they will send a client to the merchant website, and that client makes an actual purchase. Various affiliate programs offer a specific percentage of the sale as commission while others will pay you a fixed rate for every sale.