Visitors judge websites in mere milliseconds – deciding to stay or leave for aesthetic reasons alone, says Canadian researcher Gitte Lindgaard, a psychology professor at Carleton University in Ottawa, Ontario. “Unless the first impression is favorable, visitors will be out of your site before they even know that you might be offering more than your competitors.”

In the blink of eye, potential customers make up their mind about your website. Visitors' first impressions in just 50 milliseconds are also their lasting impressions – good or bad – about the quality of websites viewed, according to research just published in the British journal Behaviour & Information Technology.

The Canadian study conducted by lead researcher Gitte Lindgaard, director of the Human-Oriented Technology (HOT) Lab at Carleton University in Ottawa, Ont., resulted in a startling surprise about viewing habits by web surfers.

While most web designers knew they had very little time to make a good first impression, common wisdom suggested that surfers made up their mind in 5-15 seconds. Lindgaard says her study shows it is really just 1/20th of a second - less than the blink of an eye.

"Biologically and genetically we are hard-wired to make snap decisions," she said in an interview. If people don't like what they see, they won't stick around long enough to see what products or services a business offers. "They'll be out of there!"

The study showed 100 people a random sampling of 125 websites, flashing them on a computer monitor. In the first pass through, Lindgaard said, website images were shown at half a second (500 milliseconds). The subjects were asked to evaluate the websites on a scale of 0-100 for "totally unappealing to completely fascinating."

In the second half of the study, researchers then showed the same websites in a different random order in order to compare the first and second viewings. The results matched. "People made up their mind. Once they had decided, they stuck with it," noted Lindgaard.

In a further refinement of the study, the researched narrowed the choices to 25 of the least appealing and 25 of the most appealing website examples. The researchers again flashed the samples past the volunteer subjects, but only for 50 milliseconds this time.

"Incredible" is how Lindgaard described the results. The correlation between these results and what people loved or hated in the original test was nearly perfect – 94-98 per cent accurate.

This new study resulted from the notion of "user satisfaction" with websites. Wanting to find out what created satisfaction or dissatisfaction, the researchers focused on one of the consistent elements – aesthetics.

"The bit (of the website) that's based on aesthetics is really just my body telling me whether this feels good or bad," said Lindgaard. "… that first impression is based on a physiological reaction. If that is made so quickly, then that is likely to have an impact on subsequent judgments."

In other words, even if visitors decide to stay on an "unappealing" website, they are predisposed to "selectively look for information that supports (their) hypothesis of it being no good."

As a trained psychologist, Lindgaard further contends that "unless we understand what makes a site appealing and 'nice' to be in, we won't be able to hold users there. When browsing the Internet, if people don't like what one site offers or how it looks, or if it is cumbersome to navigate, presto - the next site is just a click away."

So if internet users can give websites a thumbs up or thumbs down in less than the blink of an eye, how do web designers make sure they're not offending users visually.

That unfortunately remains the mystery factor.

The study's results did not show how to win a positive reaction from users, said the Carleton University psychology professor. "When we looked at the websites that we tested, there is really nothing there that tells us what leads to dislike or to like."

And while further research may offer more clues, she said the vagaries of personal taste would always be a limiting factor.

"If design were reducible to a set of principles, wouldn't we find an awful lot of similar houses, gardens, cars, rooms?" said Lindgaard. "You'd have no variety."