Jakob Nielsen's Alertbox for May 1996

Top Ten Mistakes in Web Design

1. Using Frames

2. Gratuitous Use of Bleeding-Edge Technology

3. Scrolling Text, Marquees, and Constantly Running Animations

4. Complex URLs

5. Orphan Pages

6. Long Scrolling Pages

7. Lack of Navigation Support

8. Non-Standard Link Colors

9. Outdated Information

10. Overly Long Download Times

For elaboration, see: Top ten mistakes in Web design - May 96 - http://www.useit.com/alertbox/9605.html

Top ten mistakes revisited - May 99 - http://www.useit.com/alertbox/990502.html
concluded that:
* All ten mistakes from 1996 are still mistakes in 1999
* Nine of the ten mistakes still cause significant usability problems and should be avoided in modern websites
* Scrolling navigation pages cause fewer usability problems these days and can be allowed if caution is taken in their design (any time you have overly long navigation pages, I would take it as a warning signal and as a requirement for usability testing)