IE annoying message and bug

Internet Explorer has a lot of "features" that are completely useless. One of them is the infamous "Can't move focus to the control because it is invisible, not enabled, or of a type that does not accept the focus.". So what?! Just return a false value! Why do you have to throw an error?
Anyway, I've stumbled upon a bug accidentally while reviewing a html control on DynamicDrive. This is the basic setup:

<style>
.div {
display:none;
}
</style>
<script>
function loadGoogle() {
 document.getElementById('div').style.display='';
 document.getElementById('iframe').src='http://www.google.com';
 return false;
}
</script>
<div class=div id=div style="">
<iframe id=iframe src="" ></iframe>
</div>
<a href="#" onclick="loadGoogle()">Click me!</a>

And it returns an error. Why? Because the javascript on Google tries to focus something:

document.f.q.focus();

But the display is cleared before changing the src. For all purposes, the div has the display set to an empty string (and you can check it with an alert right after it is set). The funny thing is, and that might come as a surprise, that if you move the display:none to the style attribute of the div, the script above doesn't return any error!

So, bottom line: attribute set in style tag or css cannot be changed dynamically without an error, while a control attribute can. What's up with that?! (Bug found on IE7.0). If you encounter this weird error, try moving the display attribute (I couldn't replicate the bug with the visibility attribute) in the control style attribute.