Transparent Browser background

Hello,
I'd like to know if there is someway to make the browser background transparent as iWeb only has options for a picture or colour for this aspect of a page. (ie a way to change/hack the template...or from within program or something)

I have tried a transparent pic...but that doesn't work...

The iWeb page is in an iframe, and needs to be transparent to look right.

I can do this by manually changing the final .html file...but this is annoying, especially as it has to be done every time the site is updated...

Thanks