What kind of form element is used in Yahoo answers
to display categories when you want to submit a question,
and when you click a category, a second box is automatically
populated with the rigth sub-categories, how is this achieved?
Note that this is not drop down list.
It looks like it's the same element as a dropdown box: <select>
It looks and acts differently from a normal dropdown because they gave each one a "size" attribute.
I have figured out a way to do it - same for drop down list.