/* These functions are used for the dropdown menus.  a 
variable is used to hold the menu items which are referenced 
using DOM.  Their visabilty is then set and can then be called
later depending on the users mouse postion */

function menu_hide()
{
	var hide = document.getElementById('dd1');    	//set variable and assign it value
	hide.style.visibility="hidden";					//modify an attribute of the value assigned to variable	    
	var hide = document.getElementById('dd2');
	hide.style.visibility="hidden";  
	var hide = document.getElementById('dd3');
	hide.style.visibility="hidden";  
	var hide = document.getElementById('dd4');
	hide.style.visibility="hidden"; 
}

function menu_show(a)
{
	var show = document.getElementById(a);
	show.style.visibility="visible";
}