Thanks for your reply.
I’ve checked and I have no width, height or padding styles on the iframe, I’m pretty sure the size of the box is being dictated directly by the Twitter widget.
The main point was that the widget is displaying fine in Chrome but in IE it has a white background, if I can remove the white background it will be fine; it’s a problem with the widget and how it is displayed in IE.
Does anyone know how to fix this?