// 菜单变换
function changeNav(navid) {
	nav_count = 8;
	for (i = 0; i < nav_count; i++)
	{
		if (i == navid) {
			document.getElementById("nav_" + i).className = "active";
		} else {
			document.getElementById("nav_" + i).className = "";
		}
	}
	
}