No, that won’t do anything at all — because element.style is not a CSS selector for an external stylesheet. What you need to do is go back to Firebug and look again at the div that contains the entire map — in this case it has a class of .mapp-container
. So that’s the selector that you need to use to style that div:
.mapp-container {
width: 325px;
height: 250px;
position: relative;
left: 650px;
top: -20px;
}
But the other thing you REALLY, REALLY need to do before making ANY changes to your theme files is create a child theme — otherwise all your changes are going to be lost when the theme is updated. I just noticed that you are using Responsive — which is a really great theme and has totally excellent support from the developer, Emil.
So check out this page on Child Themes. You might also want to visit the Responsive forums — as they are very helpful and know the theme very well.
BTW, your site is really nice looking — great job with it. I’m in California too — the Bay Area so we’re almost neighbors :)!