Helping advertisers to control marketing expenditures by governing the delivery of an advertisement over a time period. Such governing may be accomplished by (a) determining an expected cost associated with delivering the advertisement, ungoverned, over the time period; and (b) governing the delivery of the advertisement based on the expected cost and a target cost. The delivery of the advertisement may be also governed based on time remaining in the time period, budget deficits from past periods, budget surpluses from past periods, a start date and an end date associated with the advertisement, time since a start date associated with the advertisement, and/or time until an end date associated with the advertisement. The target cost may be based on a predefined budget.