保存复选框（3）

 var http_request;
 if(window.XMLHttpRequest){
  http_request=new window.XMLHttpRequest();
  if(http_request.overrideMineType){
   http_request.overrideMineType('text/plain');
   http_request.overrideMineType('text/html');
   http_request.overrideMineType('text/javascript, application/javascript');
  }
 }else if(window.ActiveXObject){
  try{
   http_request = new ActiveXObject("Msxml2.XMLHTTP");
  }catch(e){
   try{
    http_request = new ActiveXObject("Microsoft.XMLHTTP");
   }catch(e){
    alert("construct MS Ajax failed");
   }
  }
 } else {
  alert("unknow explorer");
 }
 http_request.open("GET",url,false);
 try{
  http_request.send(null);
 }catch(e){}
 
 //Ajax处理结束，无论处理成功还是失败，都恢复页面元素功能
 if(http_request.status=="200"){
  unlockAll();
  return true;
 }else{
   box.checked=null;
   alert("server not available");
   unlockAll();
   return false;
 }
 unlockAll();
}