var active_tab = 'tab1';

function tab(event, which){
    new_tab = 'tab' + which;
	last_btn = $(active_tab + '_btn');
	last_btn.className = '';
	new_btn = $(new_tab + '_btn');
	new_btn.className = 'active';
	fade(active_tab);
	appear(new_tab);
	active_tab = new_tab;
	return false;
}