In a system and method for flexibly offering on-line promotions to visitors of a website hosted by a server, when a user signs up with the website, the server collects a plurality of user data from the visitor. If a user's data matches predetermined criteria from an advertiser, then online promotions from this advertiser are included in an opt-in window displayed to the user. In some aspects, a bifurcated client/server scripting approach isolates personally identifiable information until or unless a user opts-into an offer or offers. The server dynamically generates pricing information for each advertiser according to a flexible algorithm. The flexible algorithm depends on the type and quality of user requested by the advertiser.