function qiehuan(num){
	var lis = document.getElementById("nav").getElementsByTagName("li");
	for(var id = 0;id<(lis.length/2);id++)
	{
		if(id==num)
		{
			document.getElementById("qh_con"+id).style.display="block";
			document.getElementById("mynav"+id).className="nav_on";
		}
		else
		{
			document.getElementById("qh_con"+id).style.display="none";
			document.getElementById("mynav"+id).className="";
		}
	}
}