Directory problem

(Sorry if I post on the wrong forum)

I have a site www[dot]mysite[dot]com and a directory in it "folder" for example.
When I browse the address www[dot]mysite[dot]com/folder/ I see the content of the entire directory.
Why is that?

I do not want this directory contents to be public.

there are several solutions:

For one, create an empty file - index.htm and upload it to your folder directory.

there are several solutions:

For one, create an empty file - index.htm and upload it to your folder directory.
or a index.php file and use header("Location: /displayme.htm"); to redirect to the page you want to be showing