This strip is a commentary on the commonly-seen flashing ads on websites declaring that the viewer has won something extremely valuable (in this case a convertible sports car) and all that is required to claim the prize is to click the ad. Since most people browsing the internet have become increasingly jaded toward the deceptive tactics of internet advertisers, they usually ignore these ads outright, assuming it is a scam and that they’ll be taken to a site they have no interest in without ever receiving the promised prize.
The twist in this strip is that in this case the website actually was planning to reward a visitor with a car, but since it wasn’t claimed by the visitor the company’s CEO kept it for himself. The CEO is honestly puzzled as to why someone wouldn’t claim the prize, suggesting he is obviously oblivious to the fact that their ad resembled a common scam. (Or was he?)
This strip employs the common pattern of making the reader think everything is normal until the final frame where the punch line is subtly delivered (“It was flashing and everything!”). There are also hints of parallels between this situation and “the boy who cried wolf” wherein a certain action has proven to be deceptive on so many occasions that when it is actually legitimate no one will believe it.
