// 显示导航子栏目
var statue = false;	//标记导航框状态
var layers;             //标记当前显示的导航框ID
function show_nav(layer,num){
	hidden_nav('all');       //关闭已经显示的导航框
	var obj = document.getElementById(layer);
	obj.style.visibility = "visible";
	obj.style.left = 50 + 105 * num;
	obj.style.top = 125;
	statue = true; 		//当前导航框状态变量赋值
	layers = layer	    //当前显示导航框ID赋值
}

function hidden_nav(layer){
	if(layer = 'all' && statue){
	    var obj = document.getElementById(layers);
	    obj.style.visibility = "hidden";
	}
}