A system for displaying intermediate message content over the unused area of a web browser is described. An intermediate message display process is linked to the web browser program executed on a client computer. The process monitors user activity on the client computer and identifies areas of the web browser display area that are not used. Upon detection of an unused clear space within the web browser display area, an intermediate message is displayed in the clear area of the web browser. The intermediate message could be an advertisement display provided by a third party content provider. A timer process and clear space detection routine within the intermediate message display process govern the display of the intermediate message in accordance with specified background pattern and message window dimension parameters.