Whenever I check my email online, I risk having the most annoying advertisements in human history forced on my attention. I believe they are made so mindlessly irritating on purpose, so that people notice them. Of course, I can't remember what the ads are for - in fact, one of the reasons I don't dare click on them is that it's never clear where that click will lead. It seems to be a bunch of interchangeable stuff having to do with mortgage rates or car insurance premiums.
The "classic" annoying ad - see how quickly something matures to classicism in this age of rapid information transfer - shows an animated loop of somebody dancing. Sometimes the dancer is a busty young woman; but it has also been, at times, a skeleton, a little green alien, Santa Claus, Merlin, and I forget who else. Whoever it is, dances the same steps over and over while you wonder what a bulletin about interest rates has to do with dancing. I'm not sure what incentive this ad is supposed to be offering to click on it, but I doubt that it outweighs the risk of being taken to some virus-infested, identity-stealing black hole in cyberspace.
Another "classic" is the flashing, blinking image swearing that you're the 100,000th visitor (to your own email???), and offering you a prize if you just "click here." Like heck! How many times can one person be so lucky? This is another case of "Click at your own risk."
More recently, a recognizable individual - comedian Lewis Black - has been featured in an ad in which he is shown having what looks like the mother of all conniption fits. It is a macabre image that reminds me of some of the gruesomer hallucinations depicted in the movie Jacob's Ladder. This bit of animation isn't just annoying, it's disturbing. It makes it hard to concentrate on anything else on the screen. It makes me want to surf to another page as soon as possible.
Those who sell ads on their websites should take note of how irritating some of these ads are. If the ads are causing people to avoid your site, it will impact your income. What a terrible position to be in, relying on advertising to fund your work, only to have the advertising itself make your work less fundable. The only solution I can see is to pay a little more attention to what ads your customers are putting on your site, and if one customer wants to put something there that is going to give visitors vertigo, or gooseflesh, or headaches, or the screaming heebie-jeebies, look for a different advertiser!