Trying to set up tidy URLs for my personal website, I stumbled upon the following problem. My goal was to have a document complete.html, but only use the nicer-looking /complete-URL to refer to it.

RewriteEngine On
RewriteRule ^complete /complete.html

However, this resulted in an Internal Server Error, which checking the logs turned out to be an infinite recursion. This is because the RewriteRule ^complete matches all URLs starting with complete, including, naturally, the complete.html it then redirects them to. Use RewriteRule ^complete$ to match only URLs that are precisely complete, with nothing else following.