不用专门针对IE使用onreadystatechange的检测方式，直接食用onload的检测就好了。

var iframe = document.createElement("iframe");
iframe.src = "simpleinner.htm";

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);

via: http://www.nczonline.net/blog/2009/09/15/iframes-onload-and-documentdomain/
参考: http://msdn.microsoft.com/en-us/library/cc197055(VS.85).aspx