// -------------------------------------------------------------------
function showLayer(layerName){
    if(document.getElementById){
        var targetElement = document.getElementById(layerName);
        targetElement.style.visibility = 'visible';
    }
}

// -------------------------------------------------------------------
function hideLayer(layerName){
    if (document.getElementById){
        var targetElement = document.getElementById(layerName);
        targetElement.style.visibility = 'hidden';
    }
}