Dynamic Dropdowns based on prev selection

[eluser]the_unforgiven[/eluser]
I'm looking for some help on how to dynamically show dropdowns(DD)when a user goes to the page only the main categories should show in the DD then upon selection show another new DD that shows the sub-categories of the selected categeory.

I know javascript/jQuery will be used here and after writing the following it still doesn't work so maybe i've done something wrong.


The jQuery - http://jsfiddle.net/J9uFR/
The html - http://jsfiddle.net/5Ahek/

Would some one be kind enough to help me out here, maybe show an example based what ive done and explain what each does please....

Thanks in advance!