iRobot, which sells automated cleaning machines, wanted to see if  adding a DHTML overlay alerting visitors about their robot upgrade program would increase average order size. Click here and vote to see if it worked.

Note: They tested the overlay on their main parts and accessories page because they believed a lot of those visitors were current owners looking for replacement parts. The upgrade allowed owners to purchase new machines at discounted prices but they had to call a 1-800 number or online chat with a customer service rep in order to do so.