function showLayer(layerName)  {  
document.getElementById(layerName).style.visibility='visible';
	if(layerName == 'menu_travel'){
		if((document.getElementById('selWorld')) && (document.getElementById('replaceSelect'))){
			document.getElementById('selWorld').style.visibility='hidden';
			document.getElementById('replaceSelect').style.display = '';
		}
	}
}

function hideLayer(layerName)  {  
document.getElementById(layerName).style.visibility='hidden';
	if(layerName == 'menu_travel'){
		if((document.getElementById('selWorld')) && (document.getElementById('replaceSelect'))){
			document.getElementById('selWorld').style.visibility='visible';
			document.getElementById('replaceSelect').style.display = 'none';
		}
	}
}