Stanford U studied how users establish trust/credibility on the web and found 10 guidelines, one of which is:
* Design your site so it looks professional (or is appropriate for your purpose).
We find that people quickly evaluate a site by visual design alone. When designing your site, pay attention to layout, typography, images, consistency issues, and more. Of course, not all sites gain credibility by looking like IBM.com. The visual design should match the site’s purpose.
* Avoid errors of any kind.