current="start";

// Bildwechsel
function imgOn(name) {
	 document.images["img"+name].src="/img/t_"+name+"_mo.jpg";
} 
  
function imgOff(name) {
   if(name!= current) document.images["img"+name].src="/img/t_"+name+"_na.jpg";
}

function choose(step) {

	if(current!="start" && step.lastIndexOf('b') == '-1') {
  		document.images["img"+currentImg].src="/img/t_"+currentImg+"_na.jpg";
	}
	if(step.lastIndexOf('b') == '-1')  {
		document.images["img"+step].src="/img/t_"+step+"_mo.jpg";
	}
	document.getElementById(current).style.position = "absolute";
	document.getElementById(current).style.visibility = "hidden";
	document.getElementById(step).style.visibility = "visible";
	document.getElementById(step).style.position = "relative";
	current = step;
	if (step.lastIndexOf('b')!= '-1') currentImg = step.substr(0,step.lastIndexOf('b'));
	else currentImg = step;
}