function send_request(callback, urladdress, isReturnData,isAsynchronous){ 
		//alert(urladdress);
        var xmlhttp = getXMLHttpRequest();
        xmlhttp.onreadystatechange = function(){
            	if (xmlhttp.readyState == 4) {//readystate 为4即数据传输结束
 				    try{
				    	if(xmlhttp.status == 200){
							//alert(isReturnData);
							if(isReturnData && isReturnData==true){
								callback(xmlhttp.responseText);
							}
						}else{
							callback("抱歉，没找到此页面:"+ urladdress +"");
						}
			        } catch(e){
			        	callback("抱歉，发送请求失败，请重试 " + e);
			        }
			   }
        }
        xmlhttp.open("GET", urladdress, isAsynchronous);
		xmlhttp.setRequestHeader('If-Modified-Since', '0'); //清除缓存 
		
        xmlhttp.send(null);
}

function getXMLHttpRequest() {
        var xmlhttp;
		if (window.XMLHttpRequest) {
			try {
				xmlhttp = new XMLHttpRequest();
				xmlhttp.overrideMimeType("text/html;charset=UTF-8");//设定以UTF-8编码识别数据
			} catch (e) {}
		} else if (window.ActiveXObject) {
			try {
				xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {
				try {
					xmlhttp = new ActiveXObject("Msxml2.XMLHttp");
				} catch (e) {
					try {
						xmlhttp = new ActiveXObject("Msxml3.XMLHttp");
					} catch (e) {}
				}
			}
		}
        return xmlhttp;
}
function send_request_post(callback, urladdress, params, isReturnData, isAsynchronous){ 
		//alert(urladdress);
        var xmlhttp = getXMLHttpRequest();
		var t = "1";
		var btype=getOs();
		if(isAsynchronous==false){
			if(btype=="Firefox"){
				t = "0";			
			}
		}
		if(t != "0"){
			xmlhttp.onreadystatechange = function(){
					if (xmlhttp.readyState == 4) {//readystate 为4即数据传输结束
						try{
							if(xmlhttp.status == 200){
								//alert(isReturnData);
								if(isReturnData && isReturnData==true){
									callback(xmlhttp.responseText);
								}
							}else{
								callback("抱歉，没找到此页面:"+ urladdress +"");
							}
						} catch(e){
							callback("抱歉，发送请求失败，请重试 " + e);
						}
				   }
			}
		}
		
        xmlhttp.open("post", urladdress, isAsynchronous);
        
        xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded; charset=utf-8");
        
		xmlhttp.setRequestHeader('If-Modified-Since', '0'); //清除缓存 
		
        xmlhttp.send(params);
		
		if(t == "0"){
			callback(xmlhttp.responseText);
		}
}
function getOs()    
{    
   var OsObject = "";    
   if(navigator.userAgent.indexOf("MSIE")>0) {    
        return "MSIE";       //IE浏览器   
   }   
   if(isFirefox=navigator.userAgent.indexOf("Firefox")>0){    
        return "Firefox";     //Firefox浏览器   
   }   
   if(isSafari=navigator.userAgent.indexOf("Safari")>0) {    
        return "Safari";      //Safan浏览器   
   }   
   if(isCamino=navigator.userAgent.indexOf("Camino")>0){    
        return "Camino";   //Camino浏览器   
   }   
   if(isMozilla=navigator.userAgent.indexOf("Gecko/")>0){    
        return "Gecko";    //Gecko浏览器   
   }    
}