<body onload="load()">
<iframe id="iframe" frameborder="0" scrolling="no" width="200" height="230" allowTransparency="true"></iframe>
</body>
</html>
<script type="text/javascript">
var iframe;
function load() {
iframe = document.getElementById("iframe");
iframe. onload = iframe. onreadystatechange = iframeload;
iframe.src = "http://www.thinkpage.cn/weather/weather.aspx?uid=U712864012&cid=CHBJ000000&l=zh-CHS&p=SMART&a=0&u=C&s=1&m=0&x=1&d=3&fc=&bgc=&bc=&ti=0&in=0&li=&ct=iframe";
}
function iframeload() {
if (!iframe.readyState || iframe.readyState == "complete") {
alert("Local iframe is now loaded.");
}
}
</script>
原文：http://www.cnblogs.com/wqing/p/4524603.html