//导航菜单
var current_child = null;
var current_parent = null;
var parent_sign = false;	//一级菜单的mouseover状态标记
var child_sign = false;	//二级菜单的mouseover状态标记
function show_child(id)
{
	//一级导航
	parent_sign = true;
	var parent = document.getElementById("first_nav_" + id);
	parent.className = "choose";
	if (current_parent){
		if (current_parent!=parent) current_parent.className = ""
	}else{
		current_parent = document.getElementById("first_nav_1");
		current_child = document.getElementById("second_nav_1");
		if (current_parent != parent) current_parent.className = ""
	}
	current_parent = parent;
	//二级导航
	child_sign = false;
	var child = document.getElementById("second_nav_"+id);
	if (child) child.className = "";
	if (current_child && current_child != child) current_child.className = "hide";	
	current_child = child;
}
function menu_back()
{
	if ( !parent_sign && !child_sign && current_parent!= source_parent)
	{
		show_child(source_parent);
	}
	window.clearTimeout(iTimeoutID);
}
function set_parent_sign()
{
	parent_sign = true;
}

function set_child_sign()
{
	child_sign = true;
}

function clear_parent_sign()
{
	parent_sign = false;
	iTimeoutID = window.setTimeout(menu_back,500);
}

function clear_child_sign()
{
	child_sign = false;
	iTimeoutID = window.setTimeout(menu_back,500);
}