html>
head>
script language="javascript">

function cl()
{
var xmlhttp;

if (window.XMLHttpRequest)
{
xmlhttp=new XMLHttpRequest();
}
else
{
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}


xmlhttp.open("POST","ajax2.html",true);
xmlhttp.setRequestHeader ("Content-Type","application/x- www-form-urlencoded");
//jquery YUI默認(rèn)會(huì)發(fā)送一個(gè)含有HTTP_X_REQUESTED_WITH的HTTP請(qǐng)求頭消息，因此，可以通過判斷請(qǐng)求頭中是否含有該屬性來判斷是否時(shí)ajax請(qǐng)求
xmlhttp.setRequestHeader('HTTP_X_REQUESTED_WITH', 'HTTP_X_REQUESTED_WITH');
xmlhttp.send();

xmlhttp.onreadystatechange=function()
{
if(xmlhttp.readyState==4 xmlhttp.status==200)
{
alert(xmlhttp.responseText);
}
}
}

/script>
/head>
body>
input type="button" id="bt" name="bt" value="OK" onclick="cl();" />
/body>
/html>