An electronic commerce portal (36) for electronic commerce over the World Wide Web, the portal (36) comprising a portal web site (31) and a collection of merchant web sites (33) linked to the portal (36), and merchant tools (21) to build and maintain merchant web sites (33); wherein the tools (21) include functionality to allow merchants to select products and services to be offered with an associated buyer incentive, and wherein the portal (36) operates to cause the buyer incentives to be displayed on the merchant web site (33) and on a page (40) of the postal web site (31) according to pre-determined portal rules.