If a graphic is online but nobody sees it, does it make any noise? That is one of the existential questions that was addressed at the Nielsen Norman Group's Usability Week conference in San Francisco this week.

Usability Week is a three-day session focused on Web design. The event was in New York in March, London in May, and will be in Sydney in July.

Nielsen Norman researchers presented findings from their eye-tracking studies, the latest way to tell what users see and how they react to various designs when searching the Internet.

"People really learn quickly and evolve when they're using the Web," said Kara Pernice Coyne, director of research for Neilsen Norman. "You're able to screen things out and choose what you want to look at when it comes to the Web. So we never really know which things people have purposefully recognized and decided to screen out versus not even knowing it's there."

Figuring that out a bit more precisely is the goal of the eye-tracking research. Pernice Coyne and her colleague Dr. Jakob Nielsen, principal of Nielsen Norman, led a research project in which they used a Tobii 1750 eye-tracking device to observe 255 people searching the Web. The device is able to observe retinal action and create heat maps that indicated how long users looked at various portions of the sites.

"What experts agree to is that if a user is thinking about a particular task, then they are indeed at least fixating and thinking about it," Pernice Coyne said. "That doesn't mean that they understood it."

Subjects were assigned specific tasks such as find answers to a question using Google, purchase a present for a given demographic on the JC Penney home page, or simply absorb information from New York Magazine's Web site and decide which restaurant they would like to dine in. Findings showed that navigation of a site is goal-oriented, meaning a subject absorbs information in various areas of the site based on the task they were given.

While developers agreed that users do not respond well to text-rich sites, Nielsen posited that users don't put much stock into photographs either.

"Half the Web sites in the world have this smiling lady and users just don't look at that," he said. "It's filler content that's really wasted space. It's not that 100 percent of people won't look at that but mainly those graphical elements do tend to get ignored. Ten percent of the page is where users spend most of their time."

Developers spent the day critiquing the sites that test subjects navigated and analyzing the resulting heat maps. One interesting finding was that users tend to accept blame for not being able to navigate poorly designed sites.

"People tend to be really good at anthropomorphizing the pointer on the screen thinking, 'This is me,'" Nielsen said. "So they take responsibility for not finding what they're looking for."

Since Nielsen Norman is a research firm, the crux of the conference revolved around presenting data, not really about proposing best practices or alternative methods.

"You want to talk about how to fix it?" Pernice Coyne joked when an attendee asked about a particular Web Site that performed poorly in heat tests. "Oh, we don't do that."