var xmlHttp;
/**XMLHttpRequest  */
function createXMLHttpRequest(){
   if(window.XMLHttpRequest) {  
        xmlHttp = new XMLHttpRequest();      
    } else if (window.ActiveXObject) {   
        xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");   
    } else {   
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");   
    }     
}
/**ajax 执行方法 传入要访问后台地址，该方法会将返回结果传给callback()方法*/
function executeAjax(url){

   createXMLHttpRequest();
   xmlHttp.abort() ;
   xmlHttp.open("post",url,true);
   xmlHttp.onreadystatechange = function(){
     if(xmlHttp.readyState==4){
	      if(xmlHttp.status==200) {
	          callback(xmlHttp.responseText);
	      }
     }
   }; 
   xmlHttp.send(null);
}

function executeAjaxFun(url,fun){
   createXMLHttpRequest();
   xmlHttp.abort();
   xmlHttp.open("post",url,true);
   xmlHttp.onreadystatechange = function(){
     if(xmlHttp.readyState==4){
	      if(xmlHttp.status==200) {
	          fun(xmlHttp.responseText);
	      }
     }
   }; 
   xmlHttp.send(null);
}