From Facebook Developer Wiki

Cross site sripting warning (IE8 RC):

I have a canvas page with an fb:iframe on it. In that iframe I have a fb:serverfbml tag with and fb:request-form in it. This setup with IE8, I get a cross site scripting warning.

What would be the best solution to this? Is it a bug?

I experience very strange problem: On simple pages, this works fine, but on my site it is just not being shown on the page. I checked in page source, everything seems to be fine, but there is nothing rendered on the page, just an empty space.