//导航菜单
var current_childa = null;
var current_parenta = null;
var parenta_sign = false;	//一级菜单的mouseover状态标记
var childa_sign = false;	//二级菜单的mouseover状态标记
function show_childa(id)
{
	//一级导航
	parenta_sign = true;
	var parenta = document.getElementById("firsta_nav_" + id);
	parenta.className = "choose";
	if (current_parenta){
		if (current_parenta!=parenta) current_parenta.className = ""
	}else{
		current_parenta = document.getElementById("firsta_nav_0");
		current_childa = document.getElementById("secondb_nav_1");
		if (current_parenta != parenta) current_parenta.className = ""
	}
	current_parenta = parenta;
	//二级导航
	childa_sign = false;
	var childa = document.getElementById("secondb_nav_"+id);
	if (childa) childa.className = "";
	if (current_childa && current_childa != childa) current_childa.className = "hide";	
	current_childa = childa;
}
function menu_back()
{
	if ( !parenta_sign && !childa_sign && current_parenta!= source_parenta)
	{
		show_childa(source_parenta);
	}
	window.clearTimeout(iTimeoutID);
}
function set_parenta_sign()
{
	parenta_sign = true;
}

function set_childa_sign()
{
	childa_sign = true;
}

function clear_parenta_sign()
{
	parenta_sign = false;
	iTimeoutID = window.setTimeout(menu_back,500);
}

function clear_childa_sign()
{
	childa_sign = false;
	iTimeoutID = window.setTimeout(menu_back,500);
}