Stanford’s web credibility research surveyed 4500 people and took over three years to compile, but the 10 guidelines that came out of this study are worth repeating here.

1. Make it easy to verify the accuracy of information on your site
2. Show that there is a real organization behind your site
3. Highlight the expertise in your organization and in the content and services you provide
4. Show that honest and trustworthy people stand behind your site
5. Make it easy to contact you
6. Design your site so it looks professional (or is appropriate for your purpose)
7. Make your site easy to use – and useful
8. Update your site’s content often (at least show it’s been reviewed recently)
9. Use restraint with any promotional content (eg ads, offers)
10. Avoid errors of all types, no matter how small they seem

Read the full report.