function ns(){ 
if(document.layers){ 
document.layers['firstLayer'].visibility ='hide';
document.layers['secondLayer'].visibility ='hide';
document.layers['thirdLayer'].visibility ='hide';
document.layers['fourthLayer'].visibility ='hide';
document.layers['fifthLayer'].visibility ='hide';
document.layers['sixthLayer'].visibility ='hide';}
} 
function showLayer(a){
if (document.getElementById){
document.getElementById('firstLayer').style.visibility ='hidden'; 
document.getElementById('secondLayer').style.visibility ='hidden';
document.getElementById('thirdLayer').style.visibility ='hidden';
document.getElementById('fourthLayer').style.visibility ='hidden';
document.getElementById('fifthLayer').style.visibility ='hidden';
document.getElementById('sixthLayer').style.visibility ='hidden';
document.getElementById(a).style.visibility ='visible';
} 
else if(document.all){
document.all['firstLayer'].style.visibility ='hidden';
document.all['secondLayer'].style.visibility ='hidden'; 
document.all['thirdLayer'].style.visibility ='hidden';
document.all['fourthLayer'].style.visibility ='hidden';
document.all['fifthLayer'].style.visibility ='hidden';
document.all['sixthLayer'].style.visibility ='hidden';
document.all[a].style.visibility ='visible'; 
} 
else if(document.layers){ 
document.layers['firstLayer'].visibility ='hide';
document.layers['secondLayer'].visibility ='hide';
document.layers['thirdLayer'].visibility ='hide';
document.layers['fourthLayer'].visibility ='hide';
document.layers['fifthLayer'].visibility ='hide';
document.layers['sixthLayer'].visibility ='hide';
document.layers[a].visibility ='show';
} 
}
window.onload = ns;