Nested Unordered List Show/hide Menu That Remembers Location?

I am having a few issues with a client who requires me to code their menu in JavaScript.

Here is the HTML:

Code:
<ul id="navigation">
<li class="firstElement"><a href="#">User</a>
<ul>
<li><a href="#">Manage my profile</a></li>

[Code]....

Basically i need the menu to be collapsed to the first level initially. So only the User, Admin and Company User links are visible.

When these 1st level menu items are clicked the 2nd level sub menus need to be displayed when navigated to the 1st level index page and so on for the third level menus.

I need to be able to remember the location as well so the menu stays open on the correct page.

The annoying thing is that if i was allowed to do this in Coldfusion this would only take me a little while but i don't know much JavaScript therefore am a bit stuck. I am not allowed to use libraries either such as JQuery, MooTools

Another challenge is to style the 'active' link locations.

When you are at the first level the class of the anchor needs to be selected_bg.

When in a sub of said first level the class of that selected anchor needs to be selected_bg and the first level needs to change to selected.

For the third level both the above stays the same but then the third level takes the class of selectorThird when active.