I have been trying to center the main menu which is located in my header. I want the menu to be visible and centered as my logo is centered. currently it is either on the left or right.
Depending on which header/Logo combination you are using, there may be more solutions.
Since your website is not currently available, I can not give you the appropriate code.
Anyway, the following code should help you:(Insert it into Customizing->General->Additional CSS)