Top Ten Web Design Mistakes 

1. Legibility Problems
2. Non-Standard Links
3. Flash
4. Content That’s Not Written for the Web
5. Bad Search
6. Browser Incompatibility
7. Cumbersome Forms
8. No Contact Information or Other Company Info
9. Frozen Layouts with Fixed Page Widths
10. 10. Inadequate Photo Enlargement

The whole article, of course is available at Jacob’s Website http://www.useit.com/alertbox/designmistakes.html