If our white "Welcome to domainname.com!" page, index.html, has not been replaced by another index page, then anyone going to domainname.com will still see the white page instead of some other home page.

This is the order in which the web server looks for a page to put up as the "home" page:
Please note that the capital letters do make a difference.

default.htm, index.phtml, default.php, index.php, Index.php, Index.phtml, index.cgi, index.pht, index.cgi, index.shtml, index.shtm, index.html, Index.htm, index.htm, welcome.cgi, welcome.html, index.htm, home.html, home.htm

Just delete the index.html file and anything after it in this list will then come up automatically. Notice that "Home.html" is NOT on the list and so will not show up as your home page. You would need to rename it.