Firefox: weird characters showing for some fonts on the SharePoint websites.

If the webpage shows weird characters for some icons with Firefox, it means some fonts couldn't be downloaded successfully. Use the following steps to fix:

Go into about:config and change network.http.referer.defaultPolicy and network.http.referer.defaultPolicy.pbmode from 2 ( strict-origin-when-cross-origin ) to 3 ( no-referrer-when-downgrade , used to be the old default )