Hey Caitlin,
You are actually having overlap issues in all browsers when it comes to the bottom. I have attached a screenshot of what I see in Firefox. However the logo and header overlap as you picture in your screenshot, I only see in IE7. Ironically enough, IE9 is the only one that displays both top and bottom coming close to your desired parameters. That said, when you experience issues like that in IE8, or 7, you should be able to add an IE conditional stylesheet to help with rendering when viewed on that browser version.