The Stanford Persuasive Technology Lab compiled 10 guidelines for building web credibility based on three-year research with over 4,500 participants.
Make it easy to verify the accuracy of the information on your site.
Show that there’s a real organization behind your site.
Highlight the expertise in your organization and in the content and services you provide.
Show that honest and trustworthy people stand behind your site.
Make it easy to contact you.
Design your site so it looks professional (or is appropriate for your purpose).
Make your site easy to use – and useful.
Update your site’s content often (at least show it’s been reviewed recently).
Use restraint with any promotional content (e.g., ads, offers).
Avoid errors of all types, no matter how small they seem.
– Stanford Web Credibility Research
If the above doesn’t scream, “Be a human, care about your users and your website experience,” I don’t know what does.