last_tab = 'tab1';
	last_tab_id = '1';
	function show(layerName) { 
		document.getElementById(layerName).style.display = '';
	} 
	
	function hide(layerName) { 
		document.getElementById(layerName).style.display = 'none';
	} 
	
	function show_next(tab_name,id) {
		document.getElementById(last_tab).className = 'tab'+last_tab_id;
		var curr = document.getElementById(tab_name);
		curr.className='tab_hover'+id;
		hide(last_tab+'_data');
		show(tab_name+'_data');
		last_tab=tab_name;
		last_tab_id = id;
	}