function createXMLHttpRequest() {
    var request = false;
    if(window.XMLHttpRequest) {
        request = new XMLHttpRequest();
        if(request.overrideMimeType) {
           // request.overrideMimeType('text/xml');
        }
    } else if(window.ActiveXObject) {
        var versions = ['Microsoft.XMLHTTP', 'MSXML.XMLHTTP', 'Microsoft.XMLHTTP', 

'Msxml2.XMLHTTP.7.0', 'Msxml2.XMLHTTP.6.0', 'Msxml2.XMLHTTP.5.0', 

'Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];
        for(var i=0; i<versions.length; i++) {
            try {
                request = new ActiveXObject(versions[i]);
                if(request) {
                    return request;
                }
            } catch(e) {}
        }
    }
    return request;
}

 function createXMLHttpRequest1() {
    var request1 = false;
    if(window.XMLHttpRequest) {
        request1 = new XMLHttpRequest();
        if(request1.overrideMimeType) {
            request1.overrideMimeType('text/xml');
        }
    } else if(window.ActiveXObject) {
        var versions = ['Microsoft.XMLHTTP', 'MSXML.XMLHTTP', 'Microsoft.XMLHTTP', 

'Msxml2.XMLHTTP.7.0', 'Msxml2.XMLHTTP.6.0', 'Msxml2.XMLHTTP.5.0', 

'Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];
        for(var i=0; i<versions.length; i++) {
            try {
                request1 = new ActiveXObject(versions[i]);
                if(request1) {
                	   return request1;
                }
            } catch(e) {}
        }
    }    
    return request1;
}



function ajax(xmlhttp,_method, _url, _param, _callback) {
		//提示加载
		$('myecho').style.display='';
		var xScroll, yScroll;   
  if (window.innerHeight && window.scrollMaxY) {   
    xScroll = document.body.scrollWidth; 
    yScroll = window.innerHeight + window.scrollMaxY; 
  } else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac 
    xScroll = document.body.scrollWidth; 
    yScroll = document.body.scrollHeight; 
  } else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari 
    xScroll = document.body.offsetWidth; 
    yScroll = document.body.offsetHeight; 
  } 
		$('myecho').innerHTML="<div style=\"position:absolute;top:0;left:"+(xScroll-190)+";width:190px;height:20px;background-color:#19A4A1;padding:4px;font-Size:12px;\" id=\"msgDiv\"><font color=\"#fefcfc\"><img src=\"/images/loading2.gif\">&nbsp;数据加载中 请稍候...</font></div>"
    if (typeof xmlhttp == 'undefined') return;
    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState==4 && xmlhttp.status==200) {
            _callback(xmlhttp);
             $('myecho').style.display='none';
        }
    }
    xmlhttp.open(_method, _url, true);
    if (_method == "POST") {
        xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        xmlhttp.setRequestHeader("Content-Length", _param.length);
        xmlhttp.send(_param);
    }
    else {
        xmlhttp.send(null);
    }
}