Window resize breaks menu

I know this is an easy fix, I just don’t know it. Basically I have a vertically that spans the top of my page, but if the window is too small or resized too small, the menu is broken into two parts, the part that doesn’t fit the menu forms a new line. How can this be fixed? Much thanks!

Here’s the site with the issue: [url]http://www.entertainmentengineering.com/v6.issue1/[/url]

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