Center logo in header

Hi, Such a simple task, but I can't center the logo in the header of the site. I tried the usual CSS techniques, but nothing worked properly. I'm sure many folks need this. Could you kindly explain a good way to do this that works with this theme. The sandbox url is http://www.arthope.jredweb.com I tried to find an answer in the forums but nothing showed up. thanks in advance, J