Facebook: new IFrame canvas for page tabs width is lower than 520px?

I'm developing an app for Facebook pages and, as usual, I've stumbled upon a strange bug today. I know that tab width is supposed to be 520px, but for some reason this is not happening on these new pages which are using IFrame canvas instead of the old FBML.

Here is a screenshot documenting this bug:

As you can see the content is cropped (I used overflow: hidden; to hide the scrollbars) at a total width of 504px开发者_开发百科. Any idea about how to solve it?

Just use Firebug to better inspect this. It's indeed 520px:

AND I've just visited your page on Facebook, it seems that you didn't reset the styling for your page. try this:

body {
    margin: 0;
    overflow: hidden;
    padding: 0;
}

instead of just overflow: hidden;.

Actually you are correct. The width limit is less than 520px.

You have to use a script to solve this problem. Also the overflow:hidden trick is necessary in the html and body tags.

Facebook Rulz.