A well-written classified ad can be a great way to launch your promotional campaign without spending a fortune.

Other's have someone out front screaming "buy this stuff!". These people may wander up and down street shouting buzz-words that may or may not attract people into a shop. This is equivalent of banner ads. These might get my attention, but if shop didn't produce goods, then I would lose interest fast. And if shops consistently didn't deliver what was promised, then I would probably just ignore these hawkers altogether.

A really clever shopkeeper might hire someone to run around and plaster brochures to car windows - these are also banner ads and similar things.

Very aggressive shopkeepers might hire some very entertaining jugglers to put on shows - these are strange ads which do weird things with screens. I might look, but I almost certainly won't buy. These can, however, attract many people and some of them are likely to find something in shop to purchase.

Then there are those shopkeepers which send out people to stop shoppers on street and hold an ad in front of their face (this is a pop-up). I find this rude (it's happened in real life) and simply will not buy this stuff. I relate this to people at airports (do they still exist?) who try to sell books for donation. I've never bought one because I don't want to encourage their behavior.

A pop-under would be similar to above, except ad is slipped in shopper's back pocket so they can be surprised by it later.

Gator runs around and with some sleight-of-hand changes as many ads as it can to it's own as they are being handed or shown to patrons.

I hope this is helpful in illustrating how popup advertising fits into overall promotional picture. Each webmaster must decide how to promote his or her site based upon their goals and objectives, as well as their budget and ethics. Ethical webmasters will find means to advertise which produce results without using spamming or other unacceptable means. Unethical webmasters will use whatever technique works regardless of consequences to themselves, their customers or company and others. They will often appear to have great results, but those are often temporary and fleeting.