Change Blindness

If you're interested in this there have been several submissions of pretty much exactly the same thing:

http://searchyc.com/change+blindness

http://news.ycombinator.com/item?id=1020494

http://news.ycombinator.com/item?id=1020405

http://news.ycombinator.com/item?id=995513

http://news.ycombinator.com/item?id=152842