If you really want to do this, Javascript is the way. But you might want to read some works on usability and human-computer-interaction, which are almost universally against self-acting pulldowns. Why? Because they make life difficult for anyone with physical spasms, poor eyesight, poor eye-hand coordination, or just a bad mouse. It's extra annoying when you open a pulldown just to look at what the options are and the next thing you know you are flying off to some URL you never meant to go to. Yes, clicking the "go" button is extra work, but, thanks, I like to make my browsing decisions myself rather than having the software make them for me.