A method of distributing Internet advertisements at the websites of a number of different publishers operating web sites. An advertising entity collects lists of user identifiers from each of several advertisers. In response to a user visiting one of the websites, the user identifier associated with the user is determined. It is determined if the user identifier is on one of the list. If the user identifier is on a list, an unembedded advertisement associated with the advertiser whose list contains the user's identifier is served to the user. The advertisement may be a pop-up, pop-under, or dynamic html advertisement, and if the user is not on the list, no such an ad may not be served.