if (document.layers)  {
     ns = 1; ie = 0; 
} else {
     ns = 0; ie = 1;
     }
	 
function zeigen(name)
{
 // IE 5.x und NN 6
if (document.getElementById) {document.getElementById(''+name).style.visibility = "visible";}
 // IE 4
if (document.all && !document.getElementById) {document.all[''+name].style.visibility = "visible";}
 // NN 4.x
if (document.layers) {document.layers[''+name].visibility = "show";}
}

function verbergen(name)
{
 // IE 5.x und NN 6
if (document.getElementById) {document.getElementById(''+name).style.visibility = "hidden";}
 // IE 4
if (document.all && !document.getElementById) {document.all[''+name].style.visibility = "hidden";}
 // NN 4.x
if (document.layers) {document.layers[''+name].visibility = "hide";}
}

var i = 1;
function zeigeButtonNr(button_nr){
    verbergen(eval('"' + "button" + i +'"'));
    zeigen(eval('"' + "button" + button_nr +'"'));
    i = button_nr; 
    }