Change your logobox CSS to this:
Code:
.logobox {
width: 60px;
height: 20px;
margin-left: 30px;
margin-right: 30px;
margin-top: 20px;
margin-bottom: 20px;
padding: 0;
}
Because you have fixed dimensions for both your logo and your container div, you can use the margin properties to center the logo within the div.