Keeping menu items on a single line

I am inexperienced at coding.  My HTML5 web pages contain menus with several buttons.  Depending on the visitor's device, the buttons may occupy more than one line.  I would like to force the buttons to remain on a single line.  I've tried numerous approaches, without success, including this CSS code:    ".p7DMM01-menu {white-space: nowrap; }"
You can find the menu at www.mauitradewinds.com    Please advise.