Just when does the floating ad on that Web site go from grabbing your attention to really, really irritating you?

"There is an age-old balance between annoyance and effectiveness," said Chris Lombardo, owner and creative director of Red Guitar Advertising Studios in Newbury Park.

Sometimes, the clever car ad simply begs for the user to scroll over, type in a command and watch the car perform. Other times, the flashing banner ad seems bound to trigger a fit.

There is plenty of annoying advertising out there, but some new trends in approach and technology are driving a general shift to advertising that is more personalized and less in-your-face.

"What's so great about the Internet is the personalization and interactivity," said Ginger Rosenkrans, assistant professor of advertising at Pepperdine University in Malibu. "It's one of the most measurable mediums for advertising."

No one actually knows who is paying attention to a television or billboard ad, but with online ads, it's easy to see how many people roll over or click on an ad.

The challenge for online advertising is grabbing attention by being new and different. Campaigns don't hold on to that distinction for long. New things get great click rates and then settle down as they become commonplace.

"There's definitely some attention deficit and advertising numbness because of just the bombardment factor," said John Ardis, vice president of corporate strategy for ValueClick Inc., the online marketing services company headquartered in Westlake Village.

Take banner ads — those at the top of the page and going down the side on some sites, maybe even across the bottom. Do you look at them anymore? Research from the Nielsen Norman Group says probably not.

"Banner blindness" is what happens when users go to a page, do whatever they intend to do and leave without any idea of what was in the surrounding ads.

People looking for facts will scan through the information and won't be distracted, while those focusing on content won't notice the banner ads, Jakob Nielsen of the Nielsen Norman Group said in his blog.

Good, you might think. But fewer people paying attention led to the generally reviled offspring of the banner ad — the pop-up ad.

It got attention, even if it covered what the person was trying to see. But pop-up ads have become old hat because many Internet users are now able to block them.

The evolution continues.

Today, those who follow online advertising hint that new approaches are engaging users without irritating them.

First, there's interactivity. People can roll over or click within a banner ad to learn a bit more about a product or company before clicking to the seller's site. Some ads move or even play a video clip.

Rosenkrans is a proponent of such advertising, which invites interaction. She's seen how effective it can be in her own research, particularly when targeted at the right audience.

Ads targeted to users based on their interests or activity online are more likely to get their attention, she said.

It's already happening with search engine marketing. Google is the reigning monarch of this approach, which involves throwing up ads that relate to search terms. Searching for information on a Toyota Prius? The sponsored links on the page relate to hybrids and dealers.

The idea is that if the person is looking for information on the topic, they're a likely buyer. The ads become more relevant to the user.

Now, companies can base advertising on much more than just people's search terms by following where they go and what they do online.

So-called behavioral targeting is perhaps the approach getting the most attention and money right now, Ardis said.

The research company eMarketer projects that spending on behavioral targeting will nearly double to $1 billion next year and hit $3.8 billion by 2011.

It's getting some criticism, too, from those who worry about where targeted ads begin and privacy ends.

"When you are online today, you've been labeled and tagged as this type of consumer in milliseconds," said Jeff Chester, executive director of the Center for Digital Democracy. "All of a sudden, you are exposed to a vast number of invisible salespeople who are peering over your personal details to figure out the best way to sell to you."

Gmail content scanned

When technology expert David Holtzman spoke on privacy at California Lutheran University last month, he told students about how even their Google Gmail accounts scan the content of each e-mail to offer related ads.

Facebook drew a lot of heat for its Beacon program, which tracks the actions of users on other Web sites and shares that information with others. The company recently apologized and made it so that users could turn off Beacon.

Chester said Facebook had an obligation to explain the full advertising and data-collection program to users.

"The user needs to decide how their information is going to be used, whether it's going to be used for targeting at all, which advertisers have access to it, and whether Facebook has the right to collect and analyze it," he said.

Rosenkrans said there is a responsibility on the side of the marketer to use the information wisely and build trust when using tracking information, but there also has to be some understanding on the part of the consumer that when they sign up to use an e-mail service or online social networking site, they are exchanging information. Often, that is disclosed in the user agreements that many people accept without actually reading.

Unlike the Facebook example, most online tracking these days is done anonymously using "cookies," little bits of code.

Ardis said there is a lot of misunderstanding about what a tracking cookie does. The code provides a way of following sites used and pairing them with appropriate advertising. It doesn't reveal the user's identity.

"We couldn't find that person if we wanted to," he said.

Marketing companies are presenting a trade-off of more useful ads in exchange for information on the user's online habits, Ardis said. The whole purpose is to make the process more efficient for the marketer and relevant for the consumer, he said.

"Legitimate marketers are not interested in finding out your deep, dark secrets," he said. "They're interested in not wasting their own money."

If companies don't have the ability to target ads to consumers who might want the product or service, they return to a high-volume proposition with a lot more ads that are a lot less relevant, he said.

Lombardo sees the business going to more permission-based ads. These are ads people seek out, as opposed to those they can't click off fast enough.

"We're entering an age ... where the advertising needs to be so good, we actually invite it into our lives," he said.

It's one reason that viral ads make the rounds through e-mail. People like watching the quirky or crass videos and pass them along to friends, marketing message included.

Video clips

Lombardo is carrying the permission idea into a business he co-founded called Greetingflix.com. The site lets people put their pictures into short video clips that they can post online or send to friends and family. A commercial version is in the works so that a family that went to a theme park could put their pictures in with video from that theme park and send it on.

"It's an incredible way for ... the client to be able to harness the power of having their customers do their marketing for them," he said.

As with all Web content these days, the next frontier for online advertisers is your mobile phone.

Lombardo said scenes similar to one in the movie "Minority Report," in which people walk into a store and are pitched items based on previous purchases, aren't that far off.

Using GPS, stores could offer coupons or restaurants present reviews as a person walks by.

Sponsored Web pages will probably become a bigger deal, Ardis said. A drug company might sponsor a page about high blood pressure. Also, as broadband spreads, so will the use of video.

Ardis said the next challenge will be dealing with the Internet as it becomes increasingly more fragmented.

"Consumers tend to seek out ever more narrow niches of content and communities and activities much more aligned with their needs," he said.

That allows more refined targeting, but also presents a challenge for advertisers because they have a huge number of sites to reach. That's one reason Ardis said ad networks have suddenly become the companies to buy.

Even with all the advances, don't expect annoying ads to disappear. Anyone who wants to build a brand isn't going to take that approach, but spammers will continue to send out millions of ads for the tiny response they get, Lombardo said. And banner ads flashing "You've Won!" won't go away.

"There will always be annoying ads out there," he said.

— The Associated Press contributed to this report.