In the Bloomberg JS menu the right hand menu changes when you move up and down, but not when you move 'up and right' or 'down and right' over the left hand menu. You can move to the option you want in the left menu and then move your mouse right to get the option you want without being very accurate. In the CSS version you have to move exactly out of the left hand menu option you want to get to the correct right hand menu.

This is a great example of why it sometimes takes a lot of effort to make a good front end UI. Bloomberg's version is considerably friendlier to users.