In that case I assume you mean the CSS which was automatically loaded when you installed the plugin? In which case you can find it in the admin_page.php of the current Multi-level navigation and PixoPoint Menu plugins and I think it’s in the admin_options.php file of the new beta plugin.
thanks. might be cool in the next version to have a button that restores default CSS. I am sure a lot of us mess it up while learning CSS and forget to back up the original CSS, thanks