.html referring to .htm in .htaccess

Giganews Newsgroups
Subject: .html referring to .htm in .htaccess
Posted by:  d00gle (dougbasti…@gmail.com)
Date: 24 May 2006

If you save a file, filename.htm but look up filename.html, you get an
error, a 404.

I usually remember to save them as filename.html, but sometimes I

Does anyone know what to add in .htaccess to have a filename.htm file
refer to filename.html?
Or have .html files and .htm to equate to the same file?

I' sure there's a way for the server to look for the same file with
same-filename.html or same-filename.htm in case the file can't be found.