1. A method by a platform server having a processor for processing and displaying a plurality of advertisements, the method comprising: receiving in the platform server a plurality of advertisements from one or more advertisers intended for display within an advertising section of a plurality of webpages during a session for a duration specified by the advertiser, wherein the session includes one or more page transitions among the plurality of webpages and each transition results in a different one of the plurality of webpages being the actively viewed webpage; scheduling by the platform server the received plurality of advertisements for display within the advertising section of a particular webpage of the plurality of webpages by determining at least a position, length, and repetition of each advertisement within the advertising section of the particular webpage; transmitting from the platform server to a user's computing device the scheduled advertisements to cause the display of the plurality of advertisements on the user's computing device to switch within a session based on the duration of the advertisements independently of page transitions among the plurality of webpages; and computing, by the platform server, a cost incurred by each of the one or more advertisers for display of the plurality of advertisements, the cost computed as a function of a cost-per-second (CPS) model of displaying the advertisement within the session, the cost-per-second model indicative of total duration of display of corresponding one or more advertisements within the session.