Do you mean the drop shadow? That is part of the footer background not the iframe.
Also don't use iframes. They are so lame. Not sure why that site just didn't put the content into a div. It's only like two paragraphs but now it has scroll bars because of the iframe. That's just poor web design right there.
I've mocked up my site, and a friend once created it for me.
Now I want to add and alter information. I'll check out your advise on div, hope it won't cost too many time
You will need to make the iframe larger than the object you want to display or it will display a box like line around the whole iframe. Let me know if this helps.