function btnOk() {
    if (document.getElementById("city").value == "请选择城市") {
        alert("请选择城市！");
    }
    else {
        if(window.location.href.indexOf("city.htm")>0)
        {
            window.location.href=document.getElementById("city").value+"/168/";
        }
        else if(window.location.href.indexOf("/changecity")>0)
        {
            var thisurl=window.location.href;
            var leiclass=thisurl.substring(thisurl.indexOf("fenlei168.com/")+14,thisurl.indexOf("/changecity"));
            window.location.href = document.getElementById("city").value+"/"+leiclass+"/";
        }
        else
        {
            window.location.href = document.getElementById("city").value;
        }
    }
}