function getObject(objectId) {
    if(document.getElementById && document.getElementById(objectId)) {
	// W3C DOM
	return document.getElementById(objectId);
    } else if (document.all && document.all(objectId)) {
	// MSIE 4 DOM
	return document.all(objectId);
    } else if (document.layers && document.layers[objectId]) {
	// NN 4 DOM.. note: this won't find nested layers
	return document.layers[objectId];
    } else {
	return false;
    }
}

function show(s){
for(var i=1;i<=4;i++){
getObject("nvgS_"+i).style.display = "none";
}
getObject("nvgS_"+s).style.display = "block";
}

function unShow(){
for(var i=1;i<=4;i++){
getObject("nvgS_"+i).style.display = "none";
}
}