Abstract: The present invention provides techniques for use in electronic and online advertising. Techniques are provided in which an advertiser provides information specifying a time-spaced sequence of advertisements to be targeted and served to a particular user, across a number of different devices and screens. Each advertisement in the sequence may be served to the user while the user is using a particular electronic device. The sequence of advertisements as a whole may be optimized with regard to eliciting a particular response from the user, and each advertisement may be optimized regarding its order in the sequence and the type of device or screen on which it is to be served.