function hide(layer) {
	document.getElementById(layer).style.visibility = 'hidden';
}

function show_layer(layer) {
	document.getElementById(layer).style.visibility = 'visible';
}
function activate(layer) {
        obj = document.getElementById(layer);
        aTag = obj.getElementsByTagName('a');
	aTag[0].className = aTag[0].className + ' over';
}
function deactivate(layer) {
        obj = document.getElementById(layer);
        aTag = obj.getElementsByTagName('a');
	aTag[0].className = aTag[0].className.replace(/over/, '');
}