a1_on=new Image();
a1_on.src="images/a1.gif";
a2_on=new Image();
a2_on.src="images/a2.gif";
a3_on=new Image();
a3_on.src="images/a3.gif";
a4_on=new Image();
a4_on.src="images/a4.gif";
a5_on=new Image();
a5_on.src="images/a5.gif";
a6_on=new Image();
a6_on.src="images/a6.gif";
off=new Image();
off.src="images/quadrat.gif";

var on=null; // speichert highlight kaestchen
// var aktiv muss auf jeder seite gesetzt werden 'a1' - 'a6' ; null=alle kaestchen aus
function over(dis){
	eval('document.'+dis+'.src='+dis+'_on.src;');
	on=dis;
}

function out(){
if(on!=aktiv && on!=null){
	document.images[on].src=off.src;
	}
}

function setup(){
if(aktiv!=null){
	over(aktiv);
	}
}

// -------------- menues -----------------------
var nc4=(document.layers) ? true : false;
var ie4=(document.all) ? true : false;
var nc6=(navigator.appName=="Netscape" && navigator.appVersion.charAt(0) > 4) ? true :false;

var lastmenue=null; // speichert/schaltet das letzte menue ab

function initLayer(which, what){
if(nc4){
	document.layers[which].visibility=what;
	}
if(ie4){
	document.all[which].style.visibility=what;
	}
if(nc6){
	document.getElementById(which).style.visibility=what;
	}
}

function showLayer(which){
initLayer('leer', "visible");
if(lastmenue!=null){
	out();
	initLayer(lastmenue, "hidden");
	}							
initLayer(which, "visible");		
lastmenue=which;
}

function hideAll(){
if(lastmenue!=null){
	out();
	initLayer(lastmenue, 'hidden');
	initLayer('leer', 'hidden');
	}
}