MSN Adcenter

Microsoft adCenter (formerly MSN adCenter), is the division of the Microsoft Network (MSN) responsible for MSN's advertising services. Microsoft adCenter provides pay per click advertisements.
Similar to Google AdWords, Microsoft adCenter uses both the maximum amount an advertiser is willing to pay per click (PPC) on their ad and the advertisement's click-through rate (CTR) to determine how frequently an advertisement is shown. This system encourages advertisers to write effective ads and to advertise only on searches which are relevant to their advertisement.

Microsoft adCenter allows advertisers to target their ads by restricting their ads to a given set of demographics and by increasing their bids whenever the ad is seen by a user of a certain demographic. AdCenter allows advertisers to run their ads on specific days of the week or certain times of day.