A relatively old, but interesting piece of research about how long it takes for a website visitor to form an opinion on your website - about a 20th of a second.
Why does this matter? The researchers believe that these quickly formed first impressions last because of what is known to psychologists as the "halo effect".
So with a positive impression, your visitor should cut you a bit more slack when they encounter problems.
This research was first reported in 2006. It was one of the reasons we went to such great lengths to check out the University's new design with end users. I organised emotional response tests, focus groups and surveys around this time to help us get to the current look and feel.
Steve Krug talks about something similar - the reservior of goodwill - in his book "Don't make me think". Visitors perservere with your website until their reservoir of goodwill is used up. So it seems one factor dictating the size of the reservoir will be the visitor's first impression.
First impressions count for web - BBC News article
Web users judge sites in the blink of an eye - article in Nature.com