var isnetscape6;
var isnetscape;
var isexplorer;
var visible;
var hidden;


if(document.all)
{
	isexplorer = true;
	visible = 'visible';
	hidden = 'hidden';
} else if(navigator.appName.indexOf("Netscape") != -1)
{
	if(navigator.appVersion.indexOf("5.") != -1)
	{
		isnetscape6 = true;
		visible = 'visible';
		hidden = 'hidden';
	} else {
		isnetscape = true;
		visible = 'show';
		hidden = 'hide';
	}
}


function changeLayerVisibility(layername, newVisibility)
{
	if(layername == null || layername == '') return;

	if(isnetscape)
	{
		document.layers[layername].visibility = newVisibility;
	} else if(isnetscape6)
	{
		document.getElementById(layername).style.visibility = newVisibility;
	} else if(isexplorer)
	{
		document.all[layername].style.visibility = newVisibility;
	}
}

function showLayer(layername) {
  changeLayerVisibility(layername, visible);
}
function hideLayer(layername) {
  changeLayerVisibility(layername, hidden);
}

function switchImage(imagename, filename)
{
	if(isexplorer)
	{
		document.images[imagename].src = filename;
	} else if(isnetscape) {
		document.layers['menu'].document.images[imagename].src = filename;
	} else if(isnetscape6)
	{
		document.images[imagename].src = filename;
	}
}
var activeMenu;
var lastActiveMenu;
function hideMenus()
{
	if(activeMenu == "" && lastActiveMenu != "" && lastActiveMenu != null)
	{
		hideLayer(lastActiveMenu);
		switchImage(lastActiveMenu + "image", "img/pfeil.gif");
	}
}


function showMenu(prefix)
{
	menuname = prefix;
	showLayer(menuname);
	switchImage(prefix + "image", "img/pfeilchenhi.gif");
	activeMenu = menuname;

	if(activeMenu != lastActiveMenu)
	{
		hideLayer(lastActiveMenu);
		if(lastActiveMenu != "" && lastActiveMenu != null)
			switchImage(lastActiveMenu + "image", "img/pfeil.gif");
	}
	lastActiveMenu = "";
}


function hideMenu(menuname)
{
	lastActiveMenu = activeMenu;
	activeMenu = "";
	setTimeout("hideMenus()", 500);
}