1. If you want to put a simple border, put this into the stylesheet;
Code:
#logo {
border: 1px solid #ff0000;
}
2. You can isolate just that one selector and give it it's own declarations.
Code:
#logo {
text-align: center;
}
Remember to remove the original from the combo selector declarations. However, I don't think you could align it center and add a border just around the actual gif. I believe the border with do an outline perimeter instead of an actual border. But, it's hard to say what your set up is without a URL. Maybe you're not referring to the actual logo gif that I'm thinking about.
BTW, It seems that you'll already assigned a border for your logo via the combo selector declaration...