var currentMenuName = "" ;

function show_nav(menuName)
{
	if ( currentMenuName != menuName )
	{
		if ( currentMenuName != "" )
			hide_nav(currentMenuName) ;

		div_id = menuName + "_nav";
		// alert("nav: " + div_id);

		if ( document.getElementById )
		{
			// alert("nav2: " + div_id);
			document.getElementById(div_id).style.visiblity='visible'; 
			document.getElementById(div_id).style.display='block'; 
			currentMenuName = menuName ;
		}
	}
	
}
function hide_nav(menuName)
{
	div_id = menuName + "_nav";
	// alert("nav: " + div_id);

	if ( document.getElementById )
	{
		// alert("nav2: " + div_id);
		document.getElementById(div_id).style.visiblity='hidden'; 
		document.getElementById(div_id).style.display='none'; 
		currentMenuName = "" ;
	}
	
}