How do i do this- drop down content

Please take a look at this, down on the page you will see thw word "Referanser":
pasienthandboka.no/default.asp?mode=document&documentid=1745

Click "Referanser" and some new content shows. This new content shows in the source code even before clicking "Referanser".

I want use this feature in a menu, how can I do that ?

 

The javascript:

function toggleMenu() {
	var oMenu = document.getElementById("item");
	if(oMenu.style.display == "none")
		oMenu.style.display = "block";
	else
		oMenu.style.display = "none";
}

Code (markup):

And the html:

<ul>
	<li onclick="toggleMenu();">Menu</li>
	<li id="item" style="display:none;">
		<ul>
			<li>Item 1</li>
			<li>Item 2</li>
			<li>Item 3</li>
		</ul>
	</li>
</ul>

Code (markup):

 

Thanks VimF. That did it. Great that you help me !! Green to you.

One more thing please. I want to use this on several menus beneath each other, but it will just work on one. What variables do I have to change?

So I suppose in this case the SE`s can read the links even if its not pulled down ?