A method for securely presenting an
HTML expandable display advertisement on a computer display, comprising: storing at a serving computer, an
HTML object having an identifier associated with at least one securing computer, registering at the securing computer, the expandable display advertisement, and signaling, from a displaying computer, an expansion event for the expandable display advertisement wherein the expandable display advertisement is for display on the displaying computer. Additional operations for securely presenting an expandable display advertisement on a computer display include expanding, at the displaying computer, the expandable display advertisement; and signaling, from a displaying computer, a restoring event. Using this technique, the serving computer may be within a first domain, and the securing computer within a second domain, the second domain being different from the first domain. In some cases, a registration message received by a securing computer comprises width and height dimensions of the expandable display advertisement.