Google is probably trying them because someone has linked to those pages on their website or Google is assuming their is an index page for all of your directories of which there are none.

You have two possible solutions:

1. Do a 301 redirect from the `/xyz/` to `/xyz/index.html`, etc. This will tell Google that `/xyz/` has moved to `/xyz/index.html` and to stop looking for it.

2. Tell Apache to use index.html as the index file for your directories. You can do that by placing this snippet in a file called `.htaccess` and placing it in your web root:

`DirectoryIndex index.html`

If you choose option two be sure to also use [canonical URLs][1] on your index.html pages so you avoid duplicate content issues.


  [1]: http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html