Center menu text in top nav bar

Hi experts, it seems traditional to start by telling everybody how new you are to wordpress but I’ll just skip that step and assume that you’ll judge for yourself based on what follows. I run the site http://www.desktopenglish.net .

The issue I need help with relates to the top navigation bar and has 2 elements.

1. Firstly (the lesser of my two issues), I normally use Chrome but today viewed my site in Firefox for the first time in a long time and was shocked to see that the “contact us” button was not rendering.

I figured out that this was because there was simply too much text in the nav bar and resolved the issue by changing the page name to “contact” rather than “contact us”. This seems like a crude fix and I was wondering if there was any sure way to ensure that such a problem is not occurring on other browsers or to prevent it from happening again by better knowing exactly how many characters are permissable in the nav bar or by fixing the width.

2. My second problem is the main one and, while related to the above, is somewhat more serious for me. Having changed the page title of “contact us” to “contact”, Chrome now renders a significant space on the right of the nav bar which makes the site look terribly asymmetrical. This could obviously be remedied by centering the navigation text but I cannot find where to start.

I have tried http://wordpress.org/support/topic/anyone-know-how-to-center-the-top-nav-bar ;

and http://wordpress.org/support/topic/center-navigation-menu-text , but the text in their stylesheets does not seem to correspond to mine so I have not been able to progress.

Any help on this issue would be greatly appreciated. The complete code from my navigation.css is below for reference:

[CSS moderated as per the Forum Rules. Please just post a link to your site.]