If you change css or js files on a live webserver, change the versions. Symptoms: css not taking effect or when you look at the css in the browser the changes are not there. Work-around: Do a <ctrl> – <F5> or a <ctrl>-<shift> – <F5> to force a hard refresh on browser https://css-tricks.com/strategies-for-cache-busting-css/
Add versions to css and javascript.
List of mime types
This is for type= tag in htmls and other things https://www.iana.org/assignments/media-types/media-types.xhtml