function CheckStatus(url)
        {
            XMLHTTP = new ActiveXObject("Microsoft.XMLHTTP")
            XMLHTTP.open("HEAD",url,false)
            XMLHTTP.send()
            return XMLHTTP.status==200
        }

        function NetPing()
        {
              return CheckStatus("http://www.jb51.net");
        }

function NetPing() {
    $.ajax({
        type: "GET",
        cache: false,
        url: "http://www.jb51.net",
        data: "",
        success: function() {
            Done(1);
        },
        error: function() {
            Done(0);
        }
    });

}