般来说，我们判断 iframe 是否加载完成其实与 判断 JavaScript 文件是否加载完成 采用的方法很类似：

var iframe = document.createElement("iframe");
iframe.src = "http://www.planabc.net";
if (!/*@cc_on!@*/0) { //if not IE    iframe.onload = function(){        alert("Local iframe is now loaded.");    };
} else {    iframe.onreadystatechange = function(){//ieif (iframe.readyState == "complete"){            alert("Local iframe is now loaded.");}};
}
document.body.appendChild(iframe);

　最近， Nicholas C. Zakas 文章《Iframes, onload, and document.domain》的评论中 Christopher 提供了一个新的判断方法（很完美)

var iframe = document.createElement("iframe");
iframe.src= "http://www.planabc.net";if(iframe.attachEvent){    iframe.attachEvent("onload", function(){        alert("Local iframe is now loaded.");    });
}else{    iframe.onload= function(){        alert("Local iframe is now loaded.");    };
}
document.body.appendChild(iframe);