It's a subliminal message to get you to buy aspirin. I suppose it worked. The store shelves are crammed with aspirin products. Someone's buying 'em, over and over again. Maybe it's all those brainwashed Baby Boomers.
Mediums change and so do the messages.
And while it's not really advertising-related, it does fall under the marketing umbrella. The idea is to use spamming behind HTML code to promote a Web site's placement on the results of a search engine query. So you enter some keywords and hope for the best. That's not good enough for Web sites. They want to make sure their site is high on the results list if you put in a word that relates to them in any way.