var oldId, oldBgColor;
function hiddenLayer(elem) {
//alert(elem);
document.getElementById(elem).style.visibility = 'hidden';
//lightOff();
}
function showLayer(elem) {
document.getElementById(elem).style.visibility = 'visible';}
function lightOn(elem) {
oldId = elem;
oldBgColor = document.getElementById(elem).style.background;
document.getElementById(elem).style.background = '#eeeeee';}
function lightOff() {
document.getElementById(oldId).style.background = oldBgColor;}