var layerOld = null;
function layerOpen(layer){
    if(layerOld!=null){
        document.getElementById(layerOld).style.display = "none";
        document.getElementById("link"+layerOld).className = "";
    }
    if(layerOld!=layer){
        document.getElementById(layer).style.display = "block";
        document.getElementById("link"+layer).className = "active";
        layerOld=layer;
    } else {
        layerOld = null;
    }
}