var xmlHttp;
//create xmlHttp
function createXmlHttp()
{
    // if current brower is IE
    if(window.ActiveXObject)
    {
      xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    else if(window.XMLHttpRequest)//if current brower is other brower
    {
       xmlHttp = new XMLHttpRequest();
    }
}
/*common ajax send method
 * parameter: uri is you will go page or path,
              callBackMethod is you dispose response message 
*/
function send(uri,callBackMethod)
{
  
  createXmlHttp();//create xmlHttpRequest object
  xmlHttp.onreadystatechange=callBackMethod;//dispose response message
  xmlHttp.open("get",uri,true);//open method
  xmlHttp.send(null);
}