I didn't realize that my host is using an MySQL that is wrong for the new version of WordPress, so I went through all the updating procedures, including deleting my old files, and then found out! When I reloaded my older version of WordPress back to the server, I get that error page saying I don't have an index.html file. In the WordPress files I have both an index.html file and an index.php file. I have tried putting only the index.html file up, and then only the index.php file, and then I tried renaming the .php file to .html, and nothing is working. I know I went through this struggle the first time I installed WordPress, but I can't remember how I resolved the issue.