Google liked drop down menu
<p><img src="http://sites.google.com/site/yanchengcheok/Home/google-drop-down-menu.png" alt="alt text"></p>

<p>Hello, whenever we go to Google Page and click on the "more", a menu will be dropped down. I would like to have the following effect on my web site too. May I know which JavaScript library can help me to achieve the similar effect?</p>
