Instead of writing paragraphs explaining the extract situation I will keep this simple.

When people go to www.whatever.com by default they got to www.whatever.com/index.html

If I was to provide a link like www.whatever.com/catalog without a .html or .htm just the folder address will it always got to a 404 page or is there away to set up a default page in that specific folder ?

Any help would be appreciated thank you