Typing ".com" in the address bar

This is weird. I used to be able to just type a site name and hit return without typing the ".com" and it would go to the site (i.e. just typing "apple" instead of "apple.com"). This functionality no longer works on either of my machines. One's a Powerbook running 10.3.9 with Safari 1.3 and the other is a dual 2.3 G5 running 10.4.2 with Safari 2. Any idea why this would have happened?