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Two things and even if you go with the global nav you should look at the both of them. Both are related to the configuration of your web server. If this is a dev environment and production is different, then you may or may not have to worry. But if it's production, then I would say worry.
Directory Listings and Default Page
Your web server should have a default page. Generally a list of documents in order like index.php, index.html. index.htm, default.html, default.htm, default.asp, etc. When presented with a directory instead of a file, it should look for those files in order and present/use the first one found.
As to the Directory Listings, a secure server shouldn't allow this. It's a simple configuration change to disallow directory listings. It provides an insecure environment. Even if you don't provide a link to just the directory which provides a listing, the script kiddiez will find your server/site.
If it's your server, you should solve these configuration issues; if it's a hosting provider, either they should help you through them and get them solved correctly or you should find another provider.
