Chrome/Safari/WebKit (and IE?): Overflow not being respected

Can anyone tell me why the menu at http://preview.endlesscircle.org/ expands by about 5px horizontally only in WebKit and Trident (IE) when you click the menu on "Parent Education" to view th开发者_如何学Goat page (but not FireFox)?

(Oddly enough, in Chrome, when you have the Developer Tools window open in the same window as the web page--open as a panel, the issue disappears.)

It's the only page in WebKit where the menu width expands, and in IE, it expands on that page and "Community Involvement."

The CSS for #body is:

#body
{
    margin-top:208px;
    position:absolute;
    width:925px;
    padding:0 20px 0 20px;
    overflow:hidden;
    overflow-y:visible;
}

How come in WebKit and IE the horizontal overflow is not hidden? For the life of me, I just cannot figure this one out!

---

In parent-education.css you're restating the width of body:

body 
{
    width:933px;
}

Take it out and Webkit should work fine now. I'm not able to test in IE7.