box shadow

Hi,
I used a box shadow on my Montezuma website, and it works nicely on mac osx and safari. On chrome it doesn't show at all, on pc and firefox kind of, but the menu and widgets are sticking out on the right, and on an iPad there is no shadow (and the tagline disappears and the breadcrumbs are not covering the complete width). The code I use in the MO content.css is

body {
margin: 40px 200px 40px 200px;
padding: 20px 0 0 0;
...
background: #ffffff;
box-shadow: 0 0 60px #ccc;
-moz-box-shadow: 0 0 60px #ccc;
}

I'm afraid I also messed up on the margin, since on small screens the site is only half visible on the right side. Should I maybe use a different grid then the responsive 960px margin 0?

For a moment I thought I had it nailed, but seeing the site on other screens and devices makes me feel quite lost again...
I'll keep trying, but I'd also appreciate any support very much.
Thanks,
Ilke