Icons Are Not Showing, Or Displaying Like Squares and Strange Characters

Please try to follow the instructions from this link in order to solve these errors: 

http://meyermed.com/2015/03/fix-font-awesome-icons-not-displaying/

These instructions work for all browsers and icon packs.

Basically, just adding one module in your .htaccess file

# Allow access from all domains for webfonts.
# Alternatively you could only whitelist your
# subdomains like "subdomain.example.com".
<IfModule mod_headers.c>
  <FilesMatch "\.(ttf|ttc|otf|eot|woff|font.css|css)$">
   Header set Access-Control-Allow-Origin "*"
  </FilesMatch>
</IfModule>

should be helpful to fix this issue.

Most of the users were able to solve this cross-origin problem with the solution from that article, but if that does not work for you, you will need to contact your server provider and ask them to fix cross-origin issue, as it is server oriented.