For this dropdownlist in HTML:
I would lik
As has been stated, you can't programmatically open a using JavaScript.
However, you could write your own managing the entire look and feel yourself. Something like what you see for the autocomplete search terms on Google or Yahoo! or the Search for Location box at The Weather Network.
I found one for jQuery here. I have no idea whether it would meet your needs, but even if it doesn't completely meet your needs, it should be possible to modify it so it would open as the result of some other action or event. This one actually looks more promising.