Selene Bowlby has written a post titled "15 Key Elements All Top Web Sites Should Have" which lists things every web site should have.

1. Good Visual Design
2. Thoughtful User Interface
3. Primary Navigation Above The Fold
4. Repeat Navigation In The Footer
5. Meaningful Content
6. A Solid About Page
7. Contact Information
8. Search
9. Sign-Up / Subscribe
10. A site map
11. Separate Design from Content
12. Valid XHTML / CSS
13. Cross Browser Compatibility
14. Web Optimized Images
15. Statistics, Tracking and Analytics

Most of these make sense but there are some others that I think could be added

• Findability plan
  
• Community / Social web elements
• Mobile / print versions
• Maintenance / update strategy
• Date displayed when content was last updated / reviewed

I'm sure there are a load of others that you could add but the most difficult thing is to keep up with the rate of change. Therefore I think the most important thing is to have a web platform which is easy to adapt and change over time.

Tags: Web Development, Web Design, Selene Bowlby