From Darren Chan at thecssweblog:

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Webdesigners have an average of 50 milliseconds to make an impression
We all know that with the ever shortening attention span of people these days that we only have a few seconds to catch the attention of a potential customer. Well guess what? Now we have a study that tells us that we actually have less than a few seconds. Designers have an average of 1/20th of a second to keep a viewer. How shallow no? A study conducted by Carleton University in Canada, published in Behaviour and Information Technology, and reported on by Nature.com hypothesized that websites had 500 milliseconds to make an impression. In reality we only have 50 milliseconds before the viewer passes judgement. And so there you have it, though content is still king, the trick for us is to make a lasting impression during the first 50 milliseconds of viewing. Doesn't sound that tough. The study aligned itself with the KISS philosophy, less is more. And however great your content is, the delivery makes the initial impression and sometimes it's the only chance you'll get.

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