My site was a mess! I don't know what happened, or how long it was in that condition. Some pages had the extension HTM. Others had the extension HTML. The internal links were to HTML regardless of the actual extension of the page. I don't know how this changed. Perhaps the extensions changed when I copied the files to another computer, or perhaps they changed when I switched from Geocities to Webring. It certainly made it difficult to navigate the site. I fixed up the problem, with all extensions now set at HTM.
Anybody who has linked to a page on my site with an HTML extension will need to update the link.
Now that I have the internal links fixed, I will check the links to other sites to see what needs to be updated.