SuckerTree Vertical Menu is a Scripts software developed by Dynamic Drive. After our trial and test, the software is proved to be official, secure and free. Here is the official description for SuckerTree Vertical Menu:

This is a vertical, predominantly CSS based (with a touch of JavaScript) multi-level menu. It supports as many sub levels as you desire, plus multiple Suckertree menus on the same PaGE. The CSS and JavaScript automatically adopts to your HTML code in each case.

The trick to Suckertree is a small adoptable piece of JavaScript that crawls the inner levels of a list menu and assigns the appropriate show/hide behavior to them. This differs from Suckerfish menu, which merely uses JavaScript to compensate for IE's shortcomings when it comes to CSS, so the menu is more rigid and requires manual changes to the CSS as the number of levels in your menu changes.