I think this is the best place for this article. It is so interesting. "10 Usability Nightmares You Should Be Aware Of". I read this article on the net. Hope you all also like it.
1. Hidden log-in link.
2. Pop-ups for content presentation.
3. Dragging instead of vertical navigation.
4. Invisible links.
5. Visual noise.
6. Dead end.
7. Content blocks layering upon each other.
8. Dynamic navigation.
9. Drop-Down Menus.
10. Blinking images.
Pointing the mouse instead of clicking.