function getHttpRequest()
{
	if (window.XMLHttpRequest) {
		return new XMLHttpRequest(); //Mozilla, Safari ...
	} else if (window.ActiveXObject) {
		return new ActiveXObject("Microsoft.XMLHTTP"); //IE
	} else {
		alert("Lỗi không tạo được object");
	}
}
var httpRequest=null;
var urlback = new Array(50);
function showHint(str)
{
	httpRequest=null;
	httpRequest=getHttpRequest();
	urlback.push(str);
	document.getElementById("content").innerHTML='<p>&nbsp;</p><p align="center"><img src="images/loading.gif" alt="loading..." width="16" height="16" /></p>';
	var url="response.php?"+str+"&ran="+Math.random();
	httpRequest.onreadystatechange=stateChanged;
	httpRequest.open("GET",url,true);
	httpRequest.setRequestHeader("Connection", "close");
	httpRequest.send(null);
}

function stateChanged() 
{
	var str="";
	if (httpRequest.readyState==4 || httpRequest.readyState=="complete")
	{ 
		str=str + httpRequest.responseText;
		//alert(str);
		document.getElementById("content").innerHTML= str;
	}
}
function an_hien(id)
{
	ele=document.getElementById(id);
	if (ele.style.display=="none") ele.style.display="block";
	else
	{
		ele.style.display="none";
		ele.style.height="0px";
	}
}
function go_back()
{	
	urlback.pop();
	str=urlback.pop();
	if(str!="")showHint(str);
	//alert(str);
}