function chane_body(html_name) {
    // XMLHTTPオブジェクト作成
    var req;
    var html_name;
    if(window.XMLHttpRequest) { // IE以外
        req = new XMLHttpRequest();
    } else if(window.ActiveXObject) { // IE
        try {
            req = new ActiveXObject("Msxml2.XMLHTTP");
        } catch(e) {
            req = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }

//	html_name = "mail_send.htm"
    //ブラウザのキャッシュ対策
    var dummy = (new Date()).getTime();
//switch (xhtml) {
//case 1:
//    html_name = "jigyo.htm";
//    break;
//case 2:
//    html_name = "inftbl1.htm";
//    break;
//case 3:
//    html_name = "kanren.htm";
//    break;
//case 4:
//    html_name = "mail_send.htm";
//    break;
//default:
//    alert("OTHER");
//    break;
//};
//  alert( html_name);
  var url = html_name + "?" + dummy;
 //   var url = "mail_send.htm?" + dummy;
//   alert( url);
    var objId = "main";

    req.open("GET", url, false); //true:非同期通信
//   alert( req.readyState);   
req.onreadystatechange = function() { //状態が変更されたらこの関数を呼ぶ
        if (req.readyState == 4 && req.status == 200) {

            document.getElementById(objId).innerHTML = req.responseText;
        }
    }
    req.send(""); //送信(引数はPOST用)
}