function switchMenu(curr_id, total_num)
{
    for(var i=0; i<total_num; i++)
    {
        //二级菜单
        var el = document.getElementById('menu_sub_'+i);

        if(!el) return;

        //一级菜单前面的图片
        var img = document.getElementById('menu_master_'+i);

        if(i == curr_id)
        {
	    document.getElementById('menu_div_'+i).style.backgroundColor="#F7F7F2";
            el.style.display = "block";
            img.src = "img/open.gif";
        }
        else
        {
	    document.getElementById('menu_div_'+i).style.backgroundColor="#FFFFFF";
            el.style.display = "none";
            img.src = "img/close.gif";
        }
    }
}