For one of my projects i had to make some select boxes which would work in a chain. I had 500.000 inserts in mysql which should be found easily. So i implemented 5 chained select boxes.
The first part of the project was not meant to be public so i limited my work to Firefox. But after a while the public part started and i wanted to use some ready made widgets in smarty (like my address widget with 5 chained select boxes). When i tried it in IE 6 it did not worked.