A client complained that I added a white line above his map the other week. Sure enough, there was a 3 pixel line above the map. I investigated further and it's actually in the iframe, inline, applied to the body tag.
I figured it was an anomaly at first, but then I started to look at other projects I'd used embedded iframes on. Now I'm noticing it all over the place. I found a bug report, but it's been a while. How long does it take them to get someone to tweak a stylesheet?
Example: http://curtziegler.com/sitedemo/studio960/wordpress/contact-us/
Bug report: http://codecanyon.net/item/ajax-contact-form/50846